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Nervous Tissue, Brain and Central Nerves, Spinal Cord and Spinal Nerves

What are the two primary functional divisions of the nervous system and how do they differ?

1. Sensory nervous system- detects stimuli and transmits information from receptors to the CNS 2. Motor nervous system- initiates and transmits information from the CNS to effectors.

Name the five distinguishing characteristics of all neurons.

Excitability, conductivity, secretion, extreme longevity, amitotic

What are the functions of dendrites, axon, and neurofibrils?

Dendrites conduct electrical signals toward the cell body. They receive input that they transfer to the cell body. The axon is used to make contact with other neurons, muscle cells, or gland cells. Neurofibrils give tensile support to neurons.

Which type of axonal transport is both anterograde and retrograde? What sorts of substances are transported by this method?

Fast axonal transport
Anterograde transport of vesicles, organelles, glycoproteins. Retrograde transport of used vesicles, potentially harmful agents

How are the different processes that extend from a cell body used to structurally classify neurons?

Multipolar neurons: many dendrites and single axon
Bipolar neurons: one dendrite and one axon
Unipolar neurons: single short neuron process which branches like a T
Anaxonic neurons: dendrites and no axon

What are the three connective tissue wrappings in a nerve, and what specific structure does each ensheathe?

The epineurium encloses the entire nerve. The perineurium encloses bundles of axons. The endoneurium encloses individual axons.

What is the mode of transmission in a chemical synapse?

Molecules stored in synaptic vesicles are released from the synaptic knob of a presynaptic neuron into the synaptic cleft. Some neurotransmitter diffuses across the cleft and binds receptors on the postsynaptic membrane.

If a person suffers from meningitis (an inflammation of the coverings around the brain), which type of glial cell usually replicates in response to the infection?

Microglia

Which specific type of glial cell ensheathes axons in the PNS?

Neurolemmocytes (Schwann cells)

What is the function of the myelin sheath?

The myelin sheath provides a protective insulating covering around the axon. It prevents the passage of ions through the axonal membrane and allows for faster action potential propagation.

What are the two primary factors determining the effectiveness of PNS axon regeneration?

The amount of damage and distance between site of damage and innervated structure.

What is the difference between a chemically gated channel and a voltage-gated channel in terms of how they function?

Chemically gated channels open in response to binding of a neurotransmitter. Voltage-gated channels open in response to changes in electrical charge.

What is an electrical gradient? What is a chemical gradient?

An electrical gradient is a difference in electrical charge between two areas. A chemical gradient is an unequal distribution of a substance between two areas.

The resting membrane potential is primarily established by what two structures embedded in the plasma membrane?

Sodium ion and potassium ion leak channels

How does depolarization and hyperpolarization occur in a neuron?

Depolarization occurs when cation or voltage-gated Na+ channels open, allowing positively charged Na+ to move into the neuron.
Hyperpolarization occurs when gated K+ channels open and allow K+ to move out of the neuron, or when gated Cl- channels open and allow Cl- to move into the cell.

How does a graded potential differ from an action potential in terms of the types of channels involved and where it occurs?

Graded potentials involve chemically gated channels at dendrites and the cell body. Action potentials involved voltage-gated channels at the axon.

How are EPSP graded potentials established in the receptive segment of a neuron?

Excitatory neurotransmitters bind chemically gated cation channels. More Na+ moves into neuron than K+ moves out. The inside of the cell becomes slightly more positive.

What is the significance of the threshold membrane potential in the initial segment of a neuron?

If the threshold membrane potential is reached, it initiates an action potential. If it is not reached, no action potential is generated.

What type of channels are sequentially opened in the propagation of the action depolarization? In the propagation of repolarization?

Voltage-gated Na+ channels.
Voltage-gated K+ channels.

What is the sequence of events from the arrival of an action potential at the synaptic knob until the release of neurotransmitter into the synaptic cleft?

Voltage-gated calcium ion channels are triggered to open by an action potential. Calcium ions move into the synaptic knob. They bind to proteins of synaptic vesicles, resulting in fusion of vesicles with neuron plasma membrane. Neurotransmitter is released.

How does conduction of an action potential in an unmyelinated axon and myelinated axon differ?

In an unmyelinated axon action potentials occur down the whole length of the axon. In an unmyelinated axon, action potentials only occur at neurofibril nodes. In myelinated regions Na+ quickly diffuses through axoplasm, initiating action potentials at the next neurofibril node.

What are the general characteristics of group A nerve fibers, and what functions do they normally serve?

Group A nerve fibers have the fastest conduction velocity. This is due to their large diameter and their myelination.

What are the four primary classes of neurotransmitters?

Acetylcholine, amino acids, monoamines, neuropeptides

What is the term for the type of neuromodulation that results in a greater response from a postsynaptic neuron? A lesser response?

Facilitation and Inhibition

What are the four major regions of the brain?

Cerebrum, diencephalon, brainstem, cerebellum

Where is gray matter located within the cerebrum? Within the spinal cord?

In the cerebrum the grey matter covers the surface of the brain. It is also present in small clusters inside the white matter.Grey matter in the spinal cord is located deep to the white matter.

From superficial to deepest, name the meninges and the spaces between them.

Dura mater, subdural space (potential space), arachnoid mater, subarachnoid space, pia mater

Where is the falx cerebri located, and what is its role?

The falx cerebri is located in the midsagittal plane and projects between the left and right cerebral hemispheres. It partitions the brain and provides it with support. It also provides the site for the superior and inferior sagittal sinus.

How are the lateral ventricles connected to the third ventricle?

They both connect through an opening, the interventricular foramen.

What are the three main functions of cerebrospinal fluid?

It provides buoyancy, protection, and environmental stability to the brain.

Where is CSF first produced? How does excess CSF get removed from the blood?

It is first produced by the choroid plexus in the ventricles.
It is removed from the blood after flowing into the arachnoid villi, which drain into the dural venous sinuses.

What components make up the blood-brain barrier?

Capillary endothelial cells (with tight junctions), basement membrane, perivascular feet of astrocytes

What is the function of the corpus callosum?

It provides the main method of communication between the cerebral hemispheres.

Which lobe of the cerebrum forms the superoposterior part of the hemisphere and is involved with general sensory functions?

The parietal lobe

Which lobe of the cerebrum forms the anterior part of the hemisphere and is involved with voluntary motor functions, planning and concentration, and personality?

The frontal lobe

What role does the primary motor cortex play?

Control of voluntary skeletal muscle activity

What association area allows us to identify known objects with our eyes closed?

Somatosensory association area

What portions of the brain are linked by the association tracts? The commissural tracts? The projection tracts?

Association tracts connect different regions of the cerebral cortex within the same hemisphere. Commissural tracts extend between the cerebral hemispheres.
Projection tracts link the cerebral cortex to inferior brain regions and the spinal cord.

What are the primary functions of the left cerebral hemisphere? The right?

The left hemisphere is specialized for language abilities, and sequential and analytical reasoning tasks.
The right hemisphere is involved in visuospatial relationships, imagination, artistic skill, and pattern perception.

What is the general function of the cerebral nuclei, and what are the anatomic components that make up the nuclei?

The cerebral nuclei help regulate motor output initiated by the cerebral cortex.
Globus pallidus and putamen (lentiform nucleus); caudate nucleus; claustrum; amygdaloid body

What is the function of the pineal gland? What is the function of the habenular nuclei?

The pineal gland secretes melatonin, which helps regulate the day-night cycles (circadian rhythm).
The habenular nuclei help relay signals from the limbic system to the midbrain and are involved in visceral and emotional responses to odors.

What is the general function of the thalamus?

The thalamus is the final relay point for incoming sensory information that is processed and projected to the primary somatosensory cortex. It acts as an information filter.

What is the name and general function of the autonomic respiratory center in the pons?

The pontine respiratory center helps regulate the skeletal muscles of breathing.

Where are the pyramids located and what is their function?

The pyramids are two longitudinal ridges on the anterior surface of the medulla. They house the corticospinal tracts, which send information from the brain to the voluntary muscles.

What are the three main autonomic centers located in the medulla?

The cardiac center regulates heart rate and strength of contraction.
The vasomotor center controls blood pressure.
The medullary respiratory center regulates respiratory rate.

The superior, middle, and inferior cerebellar peduncles connect the cerebellum to which parts of the brainstem respectively?

Midbrain, pons, and medulla

What are the main functions of the limbic system?

The limbic system is involved with processing and experiencing emotions.

How is the reticular activating system related to the reticular formation?

The reticular activating system is the sensory component of the reticular formation, responsible for alerting the cerebrum to incoming sensory information.

Which cranial nerves have sensory functions only?

CNI (olfactory nerve), smell;
CNII (optic nerve), vision;
CNVIII (vestibulocochlear nerve), hearing and equilibrium

What are the functions of the cervical and lumbosacral enlargements?

They house the neuronal bodies for innervation of the upper and lower limbs, respectively.

Where are the epidural, subdural, and subarachnoid spaces located? Which contains CSF?

The epidural space lies between dura mater and inner walls of the vertebra.
The subdural space is a potential space separating the dura mater from the arachnoid mater.
The subarachnoid space is deep to the arachnoid mater and contains the CSF.

What nervous system structures are found in the anterior, lateral, and posterior horns?

The anterior horn houses cell bodies of somatic motor neurons. The lateral horns contain the cell bodies of autonomic motor neurons.
The posterior horns contain the axons and sensory neurons and the cell bodies of interneurons.

What are the three types of funiculi? What are the components of each?

Posterior funiculus, lateral funiculus, anterior funiculus. All contain both motor and sensory axons.

What are the three characteristics common to most nervous system pathways?

Most pathways decussate while traveling through the white matter of spinal cord, consist of paired tracts, and are composed of two or three neurons working together.

What are the locations and functions of primary, secondary, and tertiary neurons in sensory pathways?

Primary neurons: posterior root ganglia of spinal nerves. They project to secondary neurons.
Secondary neurons: posterior horn of spinal cord or brainstem nucleus. They project to thalamus or cerebellum.
Tertiary neurons: within thalamus. They project to the primary somatosensory cortex.

What are the locations and functions of upper and lower motor neurons in motor pathways?

Upper motor neurons are found within the cerebral cortex or a nucleus within the brainstem. They synapse on lower motor neurons or interneurons.
Lower motor neurons are found within the anterior horn of the spinal cord or a brainstem cranial nerve nucleus. They project to skeletal muscles to be innervated.

What are the differences between direct and indirect motor pathways?

Direct pathways are responsible for conscious control of skeletal muscle. They take a more direct route from the brain to the spinal cord.
Indirect pathways are responsible for subconscious or unconscious control. They take a circuitous route through the brain before conducting the signal to the spinal cord.

What are the components of a typical spinal nerve?

Anterior root containing motor axons only; posterior root containing sensory axons only; smaller posterior ramus, larger anterior ramus

What are the main properties of a reflex?

stimulus required to initiate a response to sensory input,
rapid response requiring few neurons, pre-programmed and involuntary response

What are the five steps involved in activation of a reflex?

Stimulus activates a receptor.
Nerve signal travels through to the CNS.
Information from the signal is processes by interneurons.
Motor neuron transmits a nerve signal to an effector.
Effector responds to nerve signal.

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