Unit 19: Nervous System Flashcards
The central nervous system (CNS) is the “command center” which includes the brain and spinal cord. It processes and and integrates information. What is the peripheral nervous system (PNS) and how does it differ from the CNS?
The PNS consists of the cranial nerves and the spinal nerves. There are 2 divisions:
-Sensory/afferent division~> sensory receptors that detect stimuli
-Motor/efferent division~> convey impulses away from the CNS and innervates effectors (muscles & glands)
Explain the steps of touching a hot object and quickly withdrawing your hand
Sensory receptors detect the stimuli and signal the CNS, which then sends back a signal for motor neurons, which triggers the effector muscles to withdraw the hand
What are the 2 subdivisions of the motor neurons (PNS)?
Somatic: skeletal muscles
Autonomic: involuntary
-Sympathetic~> fight/flight
-Parasympathetic~> rest, relaxation
When a signal is passed through the CNS, it goes through the _______ center
integration
Describe the cell body of the neuron
Have typical organelles
(Rough ER called Nissl Bodies)
Groups/clusters in:
-CNS = nuclei (gray matter)
-PNS = ganglia
What do dendrites do?
Receive incoming messages and relay them to the cell body
What is the axon hillock?
Where the axon meets the cell body
What are Schwann cells?
Myelin sheath of the PNS
Gaps in the myelin sheath are called ______ __ ______.
Nodes of Ranvier
What are cells that support the neurons called?
Neuroglia (glial cells)
They can undergo mitosis (can cause brain tumours if uncontrolled)
Give the 4 types of neuroglia
that serve the CNS
-Oligodendrocytes: produce myelin
-Microglia: protective—can become phagocytic to inject foreign particles
-Astrocytes: surround capillaries to form part of the blood brain barrier
-Ependymal: neural epithelia, secretes cerebrospinal fluid (CSF)
Give the types of neuroglia that serve the PNS
Schwann cells: form myelin around axons in the PNS
Satellite cells: surround neuron cell bodies in the ganglia—protect/support
Structural/Anatomical and Functional are types of classification for what?
Neurons
In the context of neuron classification, what are the 3 types of structural/anatomical classification?
-Unipolar: 1 process that divides into 2: *CNS and *PNS (peripheral end has dendrites to be sensory receptors)
-Bipolar: 2 processes~> 1 axon, 1 process with dendrites (sensory for retina&nose)
-Multipolar: >2 processes, 1 axon and many dendrites (all interneurons and motor neurons)
The functional classification of neurons focuses on the direction of impulse conduction. What are the types?
Sensory/Afferent neurons: mostly unipolar, from sensory to CNS
Interneurons: within the CNS (between sensory & motor), mostly multipolar
Motor/Efferent neurons: CNS to effectors (all multipolar)
Neuronal, neuromuscular, and neuroglandular are all types of what?
Neuron junctions (synapses)
Neuronal: neuron to neuron
Neuromuscular: motor neuron to skeletal muscle
Neuroglandular: motor neuron to gland
What are the 4 parts that make up a chemical synapse between neurons?
Presynaptic neuron (brings impulse)
Axon terminal (has neurotransmitters)
Synaptic cleft
Postsynaptic neuron (receives impulse)
What are 5 things that serve as protective features for the CNS?
Bone (skull and vertebrae)
Meninges
Cerebrospinal fluid (CSF)
Blood Brain Barrier (BBB)
Cerebral Arterial Circle
The meninges are 3 layers of protective connective tissue around the brain and spinal cord. What are the layers?
Dura mater (outer)
——subdural space——
Arachnoid mater (middle)
——subarachnoid space——
Pia mater (on surface of brain and SC)
What are 2 characteristics of the dura mater layer that are different between the brain and spinal cord?
Brain dura mater (2 layers) is separated in some places to form venous (dural) sinuses, which contain blood
The dura mater layer of the spinal cord has the epidural space superficial to it, filled with fat, blood vessels, CT, etc.
The arachnoid mater layer is avascular and has an area deep to it called the _______ space, which contains _______ _______, and has web-like strands of CT to secure it to the pia mater. It has _______ _______ in the brain only, which projects into the dural sinuses.
subarachnoid, cerebrospinal fluid, arachnoid granulations
What is meningitis?
Inflammation of the meninges
Cerebrospinal fluid (CSF) surrounds the brain and spinal cord. It is in brain ventricles and the spinal canal. What are these ventricles?
2 lateral (1st & 2nd)~> in cerebrum
3rd ventricle~> in diencephalon
4th ventricle~> surrounded by pons, medulla oblongata, and cerebrum
This selectively permeable membrane is made of endothelial cells with tight junctions, wrapped around by astrocytes
Blood brain barrier
What is the cerebral arterial circle?
Arteries which form a circle at the base of the forebrain, which circles the pituitary gland and optic chiasma (where optic nerves cross). It unites the 2 major blood supplies to the brain to provide an alternate route for blood in the case of a blockage
Explain blood RETURN from the brain
Cerebral arteries
Capillaries
Cerebral veins
Dural sinuses
Superior vena cava
The cerebrum of the forebrain has 5 lobes. What are they?
(Named after the overlying bones):
Frontal
Temporal
Parietal
Occipital
Insula (deep to temporal)
What are the 3 fissures of the forebrain?
Deep grooves that separate:
Longitudinal: right and left hemispheres
Transverse: cerebellum and cerebrum
Lateral: temporal lobe from cerebrum
Gyri are ridges in the forebrain and sucli are shallow grooves. Give examples of both
Gyri: postcentral gyrus in parietal lobe, precentral gyrus in frontal lobe
Sucli: central sulcus (between frontal and parietal lobes
What are the 3 layers of the cerebrum?
Cerebral cortex (includes motor, sensory, and association areas)
Tracts (association, commissural, and projection tracts)
Basal nuclei (paired masses of gray matter (within white) that control skeletal movement)
The motor areas of the cerebral cortex are all in the frontal lobe and control skeletal movement. What are the 3 regions?
Primary motor area (precentral gyrus)
Premotor area
Broca’s area (motor speech)
Name the 4 sensory areas of the cerebral cortex
-General sensory area (pain, touch, etc): found in parietal lobe
-Vision: occipital lobe
-Auditory and olfaction: temporal lobe
-Taste and visceral sensation (full bladder, etc): insula
What are the 3 types of tracts (white matter) in the forebrain?
-Association tracts: gyrus to gyrus in same hemisphere
-Commissural tracts: gyrus to gyrus in opposite hemispheres (eg. corpus callosum)
-Projection tracts: run vertically between brain and spinal cord
The thalamus is 2 lobes connected by an intermediate mass, which serves as a relay station for impulses coming to the cortex from the spinal cord. The hypothalamus is inferior, and it is a major regulator of the internal environment (BP, HR). What are these both a part of in the brain CNS?
Diencephalon
What 3 parts make up the hindbrain?
Pons
Medulla
Cerebellum
The cardiac, vasomotor, and respiratory centers are vital for what part of the hindbrain?
The medulla
What is the limbic system?
A functional system that has nuclei in the cerebrum and diencephalon which regulates emotions and contains areas involved in memory
The reticular formation begins with nuclei in the brain stem, which involves the cortex, thalamus, and hypothalamus to form what?
The reticular activation system (RAS)
Which functional system regulates alertness and attention?
The reticular formation. Sleep occurs when it becomes inhibited
White matter in the spinal cord is made up of myelinated axons containing ascending (sensory) or descending (motor) tracts. It forms 3 columns, called what?
Dorsal column
Lateral column
Ventral column
How does blood flow to the brain posteriorly?
It goes through the:
Vertebral arteries
Basilar artery
Posterior cerebral arteries (which is part of the cerebral arterial circle)
The association areas of the cerebral cortex are in the parietal, occipital, and temporal lobes. They ________ info from memories
recognize
The 12 pairs of cranial nerves:
Oh, Once One Takes The Anatomy Final, Very Good Vacations Are Had
(1)olfactory, (2)optic, (3)oculomotor, (4)trochlear, (5)trigeminal, (6)abducens, (7)facial, (8)vestibulocochlear, (9)glossopharyngeal, (10)vagus, (11)accessory, (12)hypoglossal
Each spinal nerve has 2 points of attachment to the spinal cord. What are they?
Dorsal root: sensory neurons
Ventral root: autonomic and somatic motor neurons
What is the joining of the dorsal and ventral roots called?
Spinal nerve
In the cross section of a nerve, there are 3 types of CT wrappings. What are they?
Epineurium: around whole nerve
Perineurium: around fascicles
Endoneurium: around axon and myelin
What are the types of PNS nerve receptors?
Exteroceptors: external environment (found at body surface)
Interoceptors: internal environment (found in viscera, blood vessels, etc.)
Proprioceptors: body position, balance, and movement (found in joints, skeletal muscles, etc.)
What are the 2 subdivisions of the PNS motor (efferent) division?
Somatic: effector~> skeletal muscle
Autonomic: effector~> smooth, cardiac muscles, glands
Autonomic motor neurons have 2 successive multipolar neurons from the CNS to the effector. What are they?
1) preganglionic neuron: myelinated, cell body in brain stem or lateral horn of the spinal cord
2) postganglionic neuron: unmyelinated, cell body in autonomic ganglion
What is the overall structure of the spinal cord?
From the foramen magnum to L1/L2 (conus medullaris), then nerves continue down through vertebral foramina as cauda equina (horse’s tail), and then becomes CT down to coccyx, called filum terminale
What 3 parts make up the cross-sectional structure of the spinal cord?
Anterior median fissure & posterior median sulcus (separate cord to L & R)
Central canal
Gray matter (neurons & interneurons)
What are the parts of the gray matter in the spinal cord?
Cross bar: gray commissures
Dorsal horn (sensory)
Lateral horn (motor)
Ventral horn (motor)
What main function does the spinal cord serve?
Sensory and motor impulses, and produces reflexes (eg. withdrawal reflex)
9 pairs of the cranial nerves are mixed nerves. What does this mean?
They carry both sensory and motor neurons
How are the 31 pairs of spinal nerves (all mixed nerves) distributed along the spine?
8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccygeal
What are rami? Provide 2 examples
They are the immediate divisions of the spinal nerve.
-Dorsal ramus: innervate skin and back muscles
-Ventral ramus: forms thoracic nerves OR join up with forming nerve plexuses
What are nerve plexuses? Give some examples
Nerve networks, for example:
Cervical plexus
Brachial plexus
Lumbar plexus
Sacral plexus
What are the different types of sensory receptors?
Mechanoreceptors
Thermoreceptors
Chemoreceptors
Photoreceptors
Nociceptors
What is the difference between free nerve endings and encapsulated nerve endings in the PNS?
Free nerve endings have terminal dendrites of unipolar sensory neurons (eg. pain, root hair plexuses)
Encapsulated nerve endings have terminal dendrites enclosed in CT (eg. Meissner’s and Pacinian corpuscles)
First order neurons are unipolar neurons attached to or associated with receptors. The axon travels in the cranial/spinal nerves to the CNS. Where can their cell bodies and axons be found?
Cell bodies in:
-sensory ganglia of cranial nerves
-dorsal root ganglia of spinal cord
Axon terminals in:
-brain
-dorsal horn of spinal cord
Somatic motor neurons are single multipolar neurons. Where can they be found?
Cell bodies in ventral horn of spinal cord OR in motor nuclei of brainstem, before going to the effector
The ascending pathway (sensory) conducts impulses from general sense receptors into the brain. What are the 3 successive neurons from the receptors to the cortex?
—1st order neuron (PNS): receptor to spinal cord
—2nd order neuron (CNS): multipolar interneuron with cell body in dorsal horn of spinal cord OR medulla
—3rd order neuron (CNS): multipolar interneuron, body in thalamus, impulses to postcentral gurus (sensory cortex)
The axons of the 1st and 2nd order neurons form ascending spinal tracts. What are they?
Dorsal (posterior) Column Pathway/Tract
—free nerve endings (eg. Meissner’s)
Spinothalamic Pathway/Tract
—temperature, pain
Spinocerebellar Pathway/Tract
—proprioceptors
In which ascending spinal tract does the 2nd order neuron go directly to the cerebellum, negating the need for a 3rd order neuron?
Spinocerebellar Pathway/Tracts
Descending pathways (motor) conducts impulses impulses from the brain to the effector. What are the 2 different pathways?
Upper motor neuron (CNS): multipolar interneurons with cell bodies in cortex OR brainstem nuclei
Lower motor neuron (cell bodies in CNS and axons in PNS)
The axons of the upper motor neurons form what descending spinal tracts?
Corticospinal tracts: cell bodies in cerebral cortex
Indirect tracts: cell bodies in brainstem nuclei, receive impulses from motor cortex, basal nuclei, and cerebellum
