A change in an organism's surroundings that causes the organism to react.
Part of the the stimulus-response model. This part detects the stimuli.
The control centre - this part of the stimulus-response model processes information from the receptor and directs the effectors' action. It is also known as the regulator.
A gland or muscle that becomes active in response to nerve impulses. This is a part of the stimulus-response model.
An action or change in behavior that occurs as a result of a stimulus. This is a part of the stimulus-response model.
Part of the stimulus response model. This stage is the detection of the new stimulus, after it has been altered by the body.
The maintenance of the internal environment according to the external environment. It goes around a set point (dynamic equilibrium).
The feedback system where a stimulus triggers a response that attempts to counteract that stimulus.
The feedback system where a stimulus triggers a response that attempts to increase that stimulus.
Central nervous system
The part of the nervous system consisting of the brain and spinal cord.
Peripheral nervous system
The section of the nervous system lying outside the brain and spinal cord.
The tough, fibrous, protective covering attached to the inside of the cranium and loosely held in the vertebral column.
The web-like threads between the two other meninges, which contains cerebrospinal fluid in the spaces.
The inner, most delicate, meninge that is made up of blood vessels lines the brain and spinal cord.
A blood-like fluid (without the red and white blood cells) made in the choroid plexus in the 3rd ventricle of the brain, Which protects and supports the CNS as a shock absorber, and transports glucose, ions and oxygen to, and urea and carbon dioxide away from, the CNS.
The biggest part of the CNS. The cortex and basal ganglia are grey, and between the grey is white.
The ridges of the cerebrum.
The dips of the cerebrum.
The big crevices of the cerebrum.
The 'bridge' of white matter between the two hemispheres of the cerebrum.
Separates the two hemispheres of the cerebrum.
The lobe involved in motor function, problem solving, spontaneity, memory, language, initiation, planning, judgement, impulse control, and social and sexual behavior.
The lobe involved in perception and sensation. Contains the primary sensory area.
The lobe that controls hearing.
The lobe that controls interoceptive awareness, with links to the limbic system (the system that controls emotional responses and their control learning & memory .
Uses information from several areas of the cortex to make sense of the incoming or outgoing message.
Latin for little man. A diagram where each body part is drawn proportional to the amount of space it takes in the brain.
Used to measure brain activity.
The second biggest part of the CNS, it receives sensory information from the cerebrum, the semicircular canals of the inner ear, the eyes pressure receptors in the skin, and stretch receptors in the muscles and joints to control posture, balance and fine movements.
Part of the brain the brain stem, which relays sensory information. It contains some cranial nerves and the pneumotaxic centre.
Controls vital functions, as it contains the cardiac centre, which controls rate and force of the heart, the respiratory centre, which controls the rate and depth of breathing, and the vasomotor centre, which controls the diameter of blood vessels. It also controls sneezing, coughing, vomiting and swallowing.
It also the site of decussation (where the nerve tracts cross over).
In the centre of the brain, and controls homeostatic mechanisms - thermoregulation, hunger, osmoregulation (thirst and bladder function), the endocrine system, the autonomic nervous system, the circadian rhythm, and partially, emotions.
Nerves that contain both sensory and motor neurons. All of the 31 spinal nerves are this type. Also called peripheral nerves. The soma for the motor neurons in these nerves are within the spinal cord; the soma for the sensory neurons are contained in ganglia, just outside the spinal cord.
The entry/exit for motor neurons from the spinal cord.
The entry/exit for sensory neurons from the spinal cord.
A collection of cell bodies (soma) that form a lump.
Somatic sensory division
Takes sensory information from the skin, muscles and joints to the CNS.
Visceral sensory division
Takes sensory information from the internal organs to the CNS.
Somatic nervous system (efferent division)
Sends information to the skeletal muscles from the CNS. Uses acetylcholine as its neurotransmitter.
Autonomic nervous system (efferent division)
Sends information to involuntary muscles and glands from the CNS. The two divisions of this system dually innervate.
The division of the autonomic nervous system that controls fight-or-flight related functions. Uses noradrenaline as its neurotransmitter.
The division of the autonomic nervous system that controls relaxed functions (rest and digest), which uses acetylcholine as its neurotransmitter.
The name of the path of an involuntary and quick movement that bypasses the CNS.
Reflexes trained by repetition.
Long extensions of the cytoplasm that send an impulse away from the cell body (soma).
Short, finger-like, extensions that take messages to the cell body (soma).
Neurons with an axon and several dendrites. Make up most motor neurons.
Neurons with an axon and one dendrite. Found in places like the eyes, ears and nose.
Neurons with only an axon and no dendrites. Their cell bodies are kept to the side. They make up most sensory neurons.
Neurons that make connections between parts of the CNS. Also called associative or connective neurons.
The state of a neuron before it is changed by an action potential. The intracellular fluid (cytoplasm) in a neuron is high in K⁺ ions and negatively charged proteins, giving it a nett negative charge. The extracellular fluid (interstitial fluid) is high in Na⁺ ions. The membrane is more permeable to K⁺ ions than Na⁺ ions, creating a positive charge in the interstitial fluid, and a negative in the cytoplasm. The difference in charge is called 'membrane potential' - at rest, a neuron has a -70mV membrane potential.
The state that occurs when when a stimulus is produced above the threshold and an action potential begins. Na⁺ channels open to flood the cytoplasm with positive ions, making the cytoplasm positive, and bringing the membrane potential up +30mV.
The state that occurs after depolarisation. The K⁺ channels are opened to allow the charge to balance again, and the Na+ channels close again, and Na⁺/K⁺ pumps transfer the ions back to their original side of the membrane. The Na⁺/K⁺ pumps move excessive amounts of the ions back to their original places, so that the membrane potential drops below -70mV.
The last state of polarisation, where the ions are reset and the membrane potential is back to its original state.
The period of time after an action potential that the neuron can't send another action potential. Can be absolute or relative.
Neurons wrapped with Schwann cells to increase conduction velocity, up to 140m/s from 2m/s, using saltatory conduction (forcing the action potential to 'jump' between Nodes of Ranvier). The myelin acts like plastic around a wire, to reduce the loss of current.
The outside layer of Schwann cells, that repairs damage to the myelin fibre.
The gap between neurons. Also called the synaptic cleft.
A chemical used by a neuron to transmit an impulse across a synapse to another cell. On the other side of the synapse, it is destroyed or repackaged by enzymes.
The condition when the body reaches a core temperature of above 42°C, when enzymes start to denature.
The condition when the body reaches a core temperature of below 35°C, when enzymes become inactive.
The homeostatic mechanisms used to regulate heat loss or retention.
Basal metabolic rate
The resting metabolic rate of the body.
Receptors of heat in the body.
A nerve cell. They conduct electrical impulses, are amitotic (don't participate in mitosis), have high metabolic rates and sensitivity to oxygen and glucose, and last throughout an entire lifetime.
Cell body. Also called perikaryon.
Nodes of Ranvier
The gaps between the myelin on a neuron's axon. They allow impulses to 'jump' between them, in a process called 'saltatory conduction'.
The type of conduction that occurs between Nodes of Ranvier on a myelinated neuron.
A type of CNS supporting cell (neuroglia) with a star shape that assists in exchanges between blood capillaries and neurons. Helps to form the blood-brain barrier, between the blood and the cerebrospinal fluid (CSF) surrounding the brain.
The smallest type of neuroglial cell, they are phagocytic cells that engulf cellular debris, waste products and pathogens.
A type of neuroglial cell, they line ventricles in the brain. They assist in producing, circulating (with their cilia) and monitoring cerebrospinal fluid (CSF) in the brain and spinal cord.
A type of neuroglial cell that produces myelin in the central nervous system - the equivalent of Schwann cells in the peripheral nervous system. They can myelinate more than one neuron at a time.
These neuroglial cells in the peripheral nervous system (PNS) surround the somas of unipolar neurons. They protect and regulat nutrients these somas.
These neuroglial cells of the peripheral nervous system (PNS) are responsible for the formation of myelin. They wrap around an axon many times to form a tight sheath.
A functional group of interconnected neurons, which interconnects incoming information, forward the processed information to its appropriate destination, and process specific types of information.
A type of neural circuit, where the impulses diverge to other neurons (ie, sending messages to different parts of the central nervous system).
A type of neural circuit where separate neurons end up at the same pathway (ie, automatic vs voluntary breathing).
A type of neural circuit that sends messages backwards and forwards between the axons (ie, conciousness, muscle control).
Parallel after-discharge circuit
A type of neural circuit that splits up into different neural pathways, and then rejoins (ie, reflexes).
The posterior branches of spinal nerves, which supply the muscles of the back acting on the vertebral column and the skin covering them.
A branch of a spinal nerve, that provides sensory/motor innervation to the skin and muscles of the anteriolateral torso and extremities.
The spinal nerve branch that supplies the vertebrae, vertebral ligaments, blood vessels of the spinal cord and meninges.
Groups of nerves that join together to do a common function after they have left the spinal cord.
The plexus that consists of the ventral rami of C1-C4 and some fibers from C5, which innervates the muscles of the neck, thoracic cavity and diaphragm.
The nerve that goes to the diaphragm.
The plexus that consists of the ventral rami of spinal nerves C5, C6, C7, C8 and T1. The nerves that emerge from the brachial plexus supply the upper limb.
The plexus that contains fibres from spinal segments T12-L4, which originates from the posterior abdominal wall and ventral rami of nerves supplying the pelvic girdle and lower limbs.
The plexus that contains fibres from spinal segments L4-S4, and originates from the posterior abdominal wall and ventral rami of nerves supplying the pelvic girdle and lower limbs.
The 12 pairs of nerves arising from the brain.
In the autonomic divison of the PNS, a neuron that has its soma located in the CNS, and whose axon extends into the PNS to synapse with a second neuron at an autonomic ganglion (the second neuron's axon synapses with the target axon).
In the autonomic division of the PNS, a neuron that has its soma located in the autonomic ganglion (where a preganglionic neuron synapses with it) and whose axon synapses with the target axon.
Pores that allow the movement of ions in or out of a cell. They are gated channels, meaning they can be opened and closed. They do this in response to chemicals (like the binding of a neurotransmitter to the channel), electrical change (the changing of the membrane potential) or movement (when force is applied to near the channel).
The difference in charge across the membrane. At rest, a neuron has a charge of -70mV.
The symbol for potassium - the ion that, at a cell's resting membrane potential, is at it's highest concentration in the intracellular fluid. The cell membrane is 75x more permeable to potassium than sodium.
The symbol for sodium - the ion that, at a cell's resting membrane potential, is at it's highest concentration in the extracellular fluid.
These pumps transfer the ions back to their original side of the membrane. The pumps move excessive amounts of the ions back to their original places, so that the membrane potential drops below -70mV.
Localised, short lived changes in membrane potential. In sensory neurones they are called generator potentials.
Runaway depolarisations along axons which produce nerve impulses. They are caused by changes in membrane permeability to Na⁺ and K⁺. This type of potential follows the 'all-or-nothing' principle.
The end of an axon.
The symbol for calcium - the ion that is released in the axon terminal when stimulated by an action potential.
The slow process of crossing the synapse.
These types of post synaptic potentials are depolarisations of the post-synaptic membrane.
These types of post synaptic potentials cause hyperpolarisations of the post-synaptic membrane.
Excitatory post synaptic potentials and inhibitory post synaptic potentials can work together to effect a post-synaptic cell, which is called _________.
This type of summation includes a single synapse, which receives several stimuli over a short period of time.
This type of summation includes stimuli from several pre-synaptic cells arrive at the same time.
Shortened to ACh, this neurotransmitter is found at the neuromuscular junctions, the preganglionic fibres of the autonomic nervous system and the parasympathetic postganglionic fibres.
Also known as norepinepherine, this neurotransmitter is found in the postganglionic fibres of the sympathetic division of the autonomic nervous system.
The tissue forming the outer layer of an organ or structure in plant or animal.
Paired lateral ventricles
The ventricles deep within each cerebral hemisphere, which are separated by the septum pellucidum.
A narrow ventricle in the diencephalon, which recieves communication from lateral ventricles, and is joined to the fourth ventricle.
The area located between the midbrain and the cerebrum and consisting of the thalamus, hypothalamus, optic chiasma, and pineal body.
The cavity consisting of the ventricles of the brain and the central canal in the spinal cord.
The ventricle in the hind brain.
The type of cell that lines the central cavity. They contribute to the formation of cerebrospinal fluid.
One of the lobes of the brain, this one is responsible for vestibular function (balance) & visceral (skin) sensation.
Areas found in the frontal lobe, which direct voluntary movement.
Areas found in the parietal, temporal & occipital lobes, which receives sensory information.
Bundles of myelinated fibres in the CNS that share common origins, destinations and functions.
Myelinated nerve fibres that join different parts of the same lobe in the cerebral hemisphere.
Fibres that connect the cerebral cortex and the lower centres of the brainstem/spinal cord.
Fibres that connect corresponding hemispheres of the brain. The main one is the corpus callosum and the minor are the anterior/posterior commissures.
Part of the diencephalon. It forms the roof of third ventricle, houses the pineal body and endocrine gland, includes the choroid plexus, and forms cerebrospinal fluid.
The area of the midbrain involved in the smooth beginning of movement, which produces dopamine.
The large motor tracts in the midbrain.
The crossing over of nerve fibers of a pathway from one side of the brain to the other.
A type of interneuron that carries information from the cerebellum to the rest of the brain and spinal cord and has dendrites resembling bushes.
The inability to coordinate muscle activity during voluntary movements, resulting in shaky/tremor-like movements.
A network of cells in the brainstem that filters sensory information and is involved in controlling arousal and alertness.
The bone structure surrounding the skull.
The neuroglial cells forming a fatty coating that prevents certain substances from entering the brain.
An area above/behind the brain, which allows blood veins to span the area, from the top of the head towards the back. The arachnoid villi drain CSF into the superior one of these.
The large opening at the base of the cranium through which the spinal cord passes.
Tracts in the CNS that contain commissural fibres.
A sensory receptor that responds to mechanical disturbances, such as shape changes (being squashed, bent, pulled, etc.). Mechanoreceptors include touch receptors in the skin, hair cells, in the ear, muscle spindles, and others.
The type of sensory receptor that responds to changes in temperature. They conduct sensations along the same pathways that carry pain sensations.
The light sensory receptors in the retina- the rods and cones.
A type of sensory receptor. This type responds to water-soluble and lipid-soluble substances that are dissolved in the surrounding fluid, and monitors the chemical composition of body fluids.
The sensory receptors in the skin that give rise to the sense of pain. They respond to various forms of tissue damage and to temperature extremes.
Sensory receptors that provide information about the external environment, and are located in or near the skin.
Also called visceroceptors, these sensory receptors respond to stimuli arising within the body. They are found in the internal visceral organs.
A type of sensory receptor, these are located in the muscles and joints, and provide information about body position and movement.
A type of sensory receptor that has free or naked nerve endings, and respond chiefly to pain and temperature.
Encapsulated dendritic endings
A type of sensory receptor, consisting of a dendrite enclosed in a connective tissue capsule.
A type of encapsulated receptor for light touch.
A type of encapsulated receptor that responds to vibrations, heavy pressure and stretch.
A type of encapsulated receptor that receives information about heavy touch, pressure, stretching of the skin, and joint movements.
Muscle spindle fibres
A type of encapsulated receptor which detects stretch in muscle
Golgi tendon organs
A type of encapsulated receptor which senses movement of the tendons.
Joint kinaesthetic receptors
A type of encapsulated receptor which senses tension & movement in articular capsule of synovial joints.
The awareness of changes in the internal and external environment
The conscious interpretation of a sensation.
The region of the sensory surface that, when stimulated, causes a change in the firing rate of that neuron.
The term used when, in the presence of a constant stimulus, receptors show a reduction in sensitivity. In rapidly adapting receptors, firing rate drops off quickly. In slowly adapting receptors, firing rate decreases slowly or not at all.
A part of the eye. It is made up of the sclera, a white connective tissue layer which protects the eye & anchors extrinsic muscles, and the cornea, an anterior, transparent section, which allows light to pass through. The cornea has no blood vessels (avascular).
Also known as the uvea, this tunic includes the choroid, ciliary body and the iris.
This layer of the vascular tunic delivers oxygen and nutrients to the retina. It's dark brown pigment prevents light scattering.
This part of the vascular tunic surrounds the lens, and is made up of the ciliary muscles and processes.
Part of the ciliary body, these are an anchor for the suspensory ligaments holding the lens.
Part of the ciliary body, it secretes aqueous humor.
The pigmented layer around the pupil made up of two muscles, the sphincter pupillae and the dilator pupillae.
The smooth muscle that constricts around pupil in close vision and bright light.
The smooth muscle that increases pupil diameter in low light.
This tunic is also known as the retina. It has two layers, an outer, pigmented layer that absorbs light, and an inner layer with two types of photoreceptors - rods and cones.
The nerve that carries neural impulses from the eye to the brain.
The region at the back of the eye where the optic nerve meets the retina. It is also called the blind spot, because it contains only nerve fibers, no rods or cones, and so is insensitive to light.
A yellowish central area of the retina that is rich in cones and that mediates clear detailed vision.
The pinpoint depression in the center of the macula lutea that is the site of sharpest vision.
The crossing where the optic nerves from the two eyes at the base of the brain.
The fibre pathways between the optic chiasm and destinations in the forebrain and brainstem.
A thick, clear, gelatinous fluid found in the posterior segment of the eye (between the lens and the retina). The vitreous humor is only produced during fetal development and helps maintain intraocular pressure, which helps hold the retina in place. It also helps transmit light.
The watery liquid secreted at the ciliary body, by the ciliary processes, that fills the anterior and posterior chambers of the eye and provides support, nourishment, and waste removal for the cornea, iris, and lens. It is reabsorbed into the venous blood by the scleral venous sinus. It cycle every 90 minutes
A measurement of the fluid pressure inside the eye.
The condition caused when there is an increased intraocular pressure in the eyeball due to obstruction of the outflow of aqueous humor.
The avascular (no vessels), biconvex (is a convex shape on both sides), transparent and flexible part of the eye. It's shape is controlled by the ciliary muscles to focus light on the eye. It can lose it's transparency and create a cataract.
The bending of light when it passes through a transparent medium, because of the speed changes caused by the medium.
The membrane that separates the outer and middle ear.
The externally visible cartilaginous structure of the external ear.
External acoustic meatus
A short, curved tube that extends from the auricle to the eardrum.
Air-filled, mucosa-lined cavity in temporal bone, that vibrates sound from the tympanic membrane to the inner ear
The 'hammer' bone in the middle ear - the outermost bone in the auditory ossicular chain. One end is attached to the tympanic membrane; the other is connected to the incus.
The 'anvil' bone in the middle ear - the auditory ossicle between the malleus and the stapes.
The 'stirrup' bone in the middle ear, that transmits sound from the incus to the cochlea. One of the auditory ossicles.
The inner ear.
The cavity within the temporal bone filled with perilymph & containing the membranous labyrinth. It is made up of the vestibule, which contain the utricle & saccule, the semicircular canals, which contain the crista ampullaris, and the cochlea, which contain the cochlear duct and organ of corti.
The set of membranous tubes containing sensory receptors for hearing and balance, filled with endolymph, in the bony labyrinth.
Organ of corti
The spiral shaped hearing organ, contained in the cochlea. It's receptors are small hair, stereocilia, on basilar membrane.
A measure of how rapidly a wave oscillates. The higher this value, the greater the amount of energy in the wave, causing a higher pitch. Pitch is measured in cycles/second.
A higher value results in an increased intensity (measured in dB).
A membrane inside the cochlea which vibrates in response to sound and whose vibrations lead to activity in the auditory pathways. Higher frequency waves displace the cilia at the base (the end closest to the outside, with shorter, stiff fibres), and lower frequency waves displace the cilia at the apex (the end furthest from the outside, with long, floppy fibres).
The static equilibrium receptors, found in the walls of the saccules and utricles. They have sensory hair cells embedded in a gelatinous otolithic membrane. Otoliths float on the membrane's surface. They monitor the head's position and respond to linear acceleration.
The dynamic equilibrium receptors, found in the ampullae of the semicircular canals. Each one has support cells and hair cells embedded into a gel-like mass called the cupula.