the nervous system
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44 terms
Terms | Definitions |
|---|---|
 sensory input | function of the nervous system. uses millions of sensory receptors to monitor changes in and out of the body |
| integration | function of the nervous system. process and interprets sensory input and decides at the given moment what to do about it |
| motor output | function of the nervous system causes response to a stimuli by activating effector organs |
| central nervous system (CNS) | brain and spinal cord. the integrating and command centre of the nervous system. interprets sensory input and dictates motor resposes based on reflexes, current conditions and past experiences. |
| peripheral nervous system (PNS) | nerves that extend from spinal cord and brain. spinal nerves carry impulses to and from the spinal cord, cranial nerves to and from the brain. sensory (afferent division) carries impulses to the CNS, motor (efferent division) away from CNS to effector organs-muscles and glands and are multipolar. |
| somatic nervous system | conduct impulses from CNS to skeletal muscles. aka voluntary nervous system because we have conscious control of our skeletal muscles |
| autonomic nervous system | visceral nerve fibres that regulate activity of smooth muscle, cardiac muscle and glands.aka involuntary nervous system because we have no control over smooth or cardiac muscle or glands. |
| neurons (nerve cells) | conduct messages in the form of nerve impulses. have extreme longetivity. are amniotic (lose ability to divide, cant regenerate). have a high metabolic rate, need oxygen and glucose to survive. full of mitochondria, ribosomes, rough endoplasmic reticulum, microtubules and neurofibrils. bundles/clumps of cell bodies in CNS=nuclei, PNS=ganglia. neuron processes in CNS=Tracts PNS=nerves. (dendrites and axons) |
| dendrites | receptive regions. provide enormous surface area for recieving signals from other neurons. |
| axons | each neuron has a single axon. axon terminals at the end of these. conducting part of neurons. generates and transmits impulses. when they reach the axon terminals they release neurotransmitters which excite or inhibit neurons. |
| myelin sheath | protects and insulates neurons. those covered in myelin sheath conduct nerve impulses quicker. formed by Schwann cells! nodes of ranvier=gaps in myelin sheath. |
| multipolar neurons | 3 or more processes, one axon, rest dendrites. 99% of neurons in humans=multipolar. major neuron type in CNS |
| bipolar neurons | 2 processes. axon and a dendrite that extends from opposite side of the body. found in speal sense organs ie retina of eye and olfactory mucosa. |
| unipolar neurons | short process that forms a T shap as it breaks off into proximal and distal branches. chiefly found in ganglia of PNS (work as sensory neurons) |
| interneurons | are between motor and sensory neurons and shuttle info through CNS pathways. are in the CNS. |
| leakage or nongated channels | always open. |
| gated channels | can open and shut when needed |
| chemically gated channels | open when appropriate chemical binds |
| voltage gated channels | open and close in response to change in membrane potential |
| mechanically gated channels | open in response to physical deformation of the receptor. |
| visceral reflex arc | receptor-sensory neuron-integration centre-motor neuron-effector. two neurons involved in motor component |
| ascending pathways | conduct sensory impulses to the brain through chains of first, second and third order neurons |
| first order neurons | cell bodies reside in a ganglion. conduct impulses from cutaneous receptors of the skin and from propriorecptors to the spinal cord or brain stem where they jump the synapse to the second order neurons. impulses from the facial area transmitted cranial nerves. spinal nerves conduct somatic sensory impulses from the rest of the body to the CNS |
| second order neurons | transmit impulses to the thalamus or cerebellum where they jump the synapse |
| third order neurons | have cell bodies in the thalamus. they relay impulses to the somatosensory cortex of the cerebrum |
| descending pathways | impulses from the brain to spinal cord. divided into two groups. 1.direct pathways equivalent to pyramdal tracts and 2. indirect pathways which is everything else.motor pathways involve two neurons |
| the direct (pyramidal) pathway | oiginate in the pyramidal neurons. they send impulses through the brain stem via pyramidal tracts then synapse to the spinal cord then synapse with interneurons or ventral horn motor neurons and then activate skeletal muscles. fast and fine movements. |
| mechanoreceptors | respond to mechanical force such as touch, pressure, vibration and strech |
| thermoreceptors | sensitive to temp changes |
| photoreceptors | such as the retina of the eye respond to light energy |
| chemoreceptors | respond to chemicals in solution |
| nocioreceptors | respond to potentially damaging stimuli that result in pain- intense heat (hot or cold), excessive pressure, inflammatory chemicals. |
| externoreceptors | sensitive to stimuli outside the body and are at or below surface |
| interoreceptors | respond to stimuli within body |
| proprioceptors | respond to stimuli within body, but location is restricted to skeletal muscle, tendons, joints, ligaments and connective tissue coverings of bones and muscles. |
| reflex arc | rapid, predictable motor response to a stimulus. -receptor -sensory neuron -integration centre -motor neuron -effector |
| spinal reflex | a somatic reflex mediated by the spinal cod. ie stretch reflex: knee jerk reaction |
| depolarisation | reduction in membrane potential (inside of membrane becomes LESS negative, ie -75 to -60 mV) |
| hyperpolarisation | increase in membrane potential, becoming more negative then the resting potential (ie -70 to -75 mV) |
| graded potential | shortlived changes in membrane potential. either depolarisation or hyperpolarisation. triggered by a change in a neuron's environment that causes gated ion channels to open. |
| action potential (AP) | brief reversal of membrane potential with a total amplitude of about 100 mV (-70mV to +30mV) -depolarisation (-70mV to +30mV) -repolarisation (+30mV to -90mV) -hyperpolarisation (-90mV to -70mV) |
| synapse | a junction that mediates impulses rom one neuron to the next or a neuron to an effector cell. |
| electrical synapse | less common. have protein channels. found in the brain |
| chemical synapse | made up of axon terminal and a neurotransmitter receptor region -AP arrives at axon terminal -voltage gated Ca+ channels open and Ca+ enters axon terminal -Ca+ causes neurotransmitter containing vesicles to release their contents by exocytosis -neurotransmitter diffuses across the synaptic cleft and binds to receptors on post synaptic cleft -binding opens ion channels resulting in graded potentials -neurotransmitter effects are terminated |
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