Module 5 - Central Nervous System Flashcards
1
Q
What are the 2 primary divisions of the nervous system?
A
Central nervous system and peripheral nervous system
2
Q
What does the central nervous system consist of?
A
Brain and spinal cord
3
Q
What does the peripheral nervous system consist of?
A
Nerve fibers carrying information between the CNS and other parts of the body
4
Q
What are the subdivisions of the PNS and what are they responsible for?
A
Afferent division - carries information to the CNS informing it of changes in the external and internal environments
efferent division - carries information from the CNS to the effector organs (muscles or glands) that bring about the desired effect
5
Q
What are the 2 subdivisions of the efferent nervous system and what are they responsible for?
A
somatic nervous system - controls skeletal muscle
autonomic nervous system - controls smooth muscles, cardiac muscle and glands
6
Q
What are the 2 subdivisions of the autonomic nervous system?
A
Sympathetic nervous system and parasympathetic nervous system
7
Q
What are the 3 functional classes of neurons?
A
Afferent neurons, efferent neurons, and interneurons
8
Q
What is an effector organ?
A
Muscle or gland
9
Q
Describe afferent neurons
A
• Located primarily in PNS
• Have a sensory receptor at its peripheral end
• Cell body located adjacent to the spinal cord
• Peripheral axon
o Also called afferent fiber
o Long and extends from receptor to cell body
• Central axon
o Short and passes information from the cell body to the spinal cord
o Only portion that goes into the CNS
o Synapses with other neurons in the spinal cord
10
Q
Describe efferent neurons
A
• Located primarily in PNS
• Cell bodies originate in CNS
o Presynaptic inputs from CNS synapse with efferent neuron in CNS
o Integrate information from many presynaptic neuron inputs
• Efferent axon
o Also called efferent fiber
o Travel out of CNS
o Connects with effector organ
• Autonomic nervous system
o Have 2 neuron chain between CNS and effector organs
11
Q
Describe interneurons
A
- Lie entirely within the CNS
- Estimated more than 100 billion
- Reflex arc is an example of a simple connection between afferent and efferent neurons
- The more complex the required action, the greater the number of interneurons involved
- Interconnections between interneurons are responsible for thoughts, emotions, etc.
12
Q
What is cognition?
A
The act or process of knowing, including both awareness and judgement
13
Q
What are the 3 parts of the spinal cord?
A
Midbrain, pons, and medulla
14
Q
Why are the processes performed by the brainstem referred to as vegetative processes?
A
Because they are performed unconsciously
15
Q
What is attached to the top rear of the brainstem?
A
The cerebellum
16
Q
What does the brainstem control?
A
Life-sustaining processes such as respiration, circulation, and digestion
17
Q
What does the cerebellum control?
A
Maintaining proprioception and subconscious coordination of movement. Also plays role in learning skilled motor tasks
18
Q
What is the term for maintaining proper position of the body in space?
A
Proprioception
19
Q
What is located superior to the brainstem and within the interior of the cerebrum?
A
Diencephalon
20
Q
What are the parts of the diencephalon?
A
Thalamus, epithalamus and hypothalamus
21
Q
What is the main function of the hypothalamus?
A
Part of the endocrine system controlling many homeostatic functions
22
Q
What is the basic function of the thalamus?
A
- Relay center for impulses (except smell)
* Directs sensory impulses to specific areas of the brain for interpretation
23
Q
What is the most superior portion of the brain?
A
Cerebrum
24
Q
How much of the brain weight does the cerebrum account for?
A
80%
25
What is the outer layer of the cerebrum called?
Cerebral cortex
26
What is the inner core of the cerebrum called?
Basal ganglia
27
What are the main functions of the cerebrum?
o Higher functioning, reasoning, memory, intelligence etc.
| o Voluntary motor actions and sensory processing
28
What is a neuroglial cell and what are their main functions in the CNS?
* Also referred to as glial cells
* Smaller and more numerous than neurons
* Continue to divide throughout lifetime
* Do not conduct impulses
* Communicate with neurons and other glial cells via chemical messengers
* Serve as connective tissue of CNS
* Support neurons by maintaining homeostatic environment
* Modulate synaptic function to help with learning and memory
29
What is the most abundant glial cell in the CNS?
Astrocyte
30
What serves as the main connective tissue in the CNS?
Astrocytes
31
How do astrocytes serve the developing embryo?
• In the embryo they secrete chemicals that regulate growth, migration, and interconnections among neurons in the brain
32
What neuroglia cell is important to the repair of brain injuries and neural scar formation?
Astrocytes
33
How do astrocytes maintain the chemical environment needed for the proper generation of nerve impulses?
o Regulate concentration of ions such as potassium
o Uptake excess neurotransmitters
Glutamate
Gamma-aminobutyric acid (GABA)
Excitatory and inhibitory neurotransmitters
34
What would happen if the astrocytes did not uptake any excess potassium in the brain?
It would lower the concentration gradient of K+ between ICF and ECF, this would bring the cell closer to threshold level, even at rest, increasing excitability of the brain
May be a factor behind epileptic seizures
35
How do astrocytes play a roll in learning and memory?
o Influence formation of neural synapses
o Gap junctions connect astrocytes to each other and to neurons
Allows chemical signal to pass without entering ECF
o Have receptors for glutamate or ATP released by neurons
Leads to K+ influx into glial cell
Rise in K+ causes glial cell to release ATP
Other glial cells sense the ATP in the ECF or K+ through gap junctions allowing them to talk to each other about activity
36
Why do some neuroscientists believe that synapses should be considered 3-party junctures?
Because the synapse involves the glial cells as well as traditional pre and post synaptic neurons
37
Describe oligodendrocytes in the CNS.
• Multiple long processes wrap many times around axons forming the myelin sheath in CNS
• Do not possess regenerative properties
• Synthesize proteins to prevent axon growth
o May serve to keep axons from growing where they shouldn’t
38
Describe microglial cells, their function, as well as their active and resting states
• Also called microgliocytes or microglia
• Functions as phagocytes
• Originate in bone marrow and migrate into CNS during embryo development
o Remain stationary until activated by infection or injury
• When resting
o Wispy cells with long branches radiating out
o Release low levels of nerve growth factor for neurons and other glial cells
• When activated
o Branches retracted, become round and highly mobile
o Move to infected area to remove invaders or debris
o Release destructive chemicals against target
39
What are cilia, what cell type in the brain have these, and what is their function?
Short, brush like projections continuous with the surface membrane
Located on ependymal cells
Beat rhythmically back and forth contributing to flow of CSF through ventricles
40
What provides structure to the cilia and the protein required for the function of the ependymal cells
Microtubules and dynein
41
What cell type in the CNS can serve as a neural stem cell with the potential for not only forming other glial cells but neural cells as well?
Ependymal cells, but we haven't figured out how to turn it on
42
What are the most common forms of brain tumors of neural origin and why?
Glial tumors or gliomas because glial cells do not lose the ability to replicate
43
What are the 2 types of brain tumors that are non-neural in origin?
Cancer cells that metastasize to the brain from other sites
| Meningiomas made from the meninges
44
What are the 4 main features that help protect the CNS from injury?
Cranium and vertebral column
Meninges
CSF
Blood-brain barrier
45
Describe the dura mater
• Outermost layer
• Tough mother
• Thick and strong made of dense irregular connective tissue
• Formed by 2 layers separated only by the dural or venous sinuses
• Continuous with the epineurium
o Outer covering of spinal and cranial nerves
46
Describe the arachnoid mater
```
• Middle layer
• Thin and avascular
• Epithelioid arrangement of cells
• Spiderweb arrangement
• Delicate, cellular covered collagen (and some elastic) fibers
• Fibers extend to pia mater
• Arachnoid villi
o Protrusions of arachnoid tissue
o Penetrates gaps in dura and project to dural sinuses
```
47
What does the subarachnoid space contain?
CSF
48
Describe the pia mater
• Innermost layer
• Adheres to spinal cord and brain
• Thin transparent epithelioid connective tissue
o Squamous to cuboidal cells
• Bundles of collagen and fine elastic fibers interlace cells
• Many blood vessels provide oxygen and nutrients to brain and spinal cord
o Comes in close contact with ependymal cells, important for CSF formation
49
What primarily makes the CSF?
Choroid plexus that lines the walls of ventricles
50
How does CSF work as a shock absorber for the brain?
o Same density as brain so it remains suspended
51
How does the CSF composition help provide the specific chemical environment needed for neuronal signaling?
o Lower K+ and higher Na+ than plasma
| o Ideal for ions moving down concentration gradient during nerve impulses
52
Where are the 4 ventricles for CSF in the brain located?
• Left and right lateral ventricle
o Separated anteriorly by the septum pellucidum
• Third ventricle
o Narrow cavity along midline between left and right halves of the thalamus
• Fourth ventricle
o Between pons/medulla and cerebellum
53
Describe the circulation of CSF
• Ependymal cells are ciliated helping to move the CSF around
• CSF is continuously added from choroid plexus of each ventricle
• Fluid starts at left and right lateral ventricles
• Goes through interventricular foramina into third ventricle
• Goes through aqueduct of midbrain
o Also called the cerebral aqueduct
• Takes CSF through midbrain into fourth ventricle
• Small amount of CSF goes through central canal of spinal cord
• Majority enters the subarachnoid space through
o Single median aperture
o Paired lateral apertures
• CSF then circulates in subarachnoid space around surface of brain and spinal cord
54
How is CSF reabsorbed?
• Reabsorbed at the same rate as it is created
• Arachnoid granulations or arachnoid villi
o Finger like projections head into dural venous sinus
• Blood and lymphatic capillaries in pia mater
55
What is the pressure of the CSF and what can happen if some fluid is removed?
• CSF pressure is 10 mmHg, small reduction for spinal tap can produce severe headaches
56
What is the total volume of CSF in the average adult? How often is this volume replaced?
• Entire volume is 125-150 mL of fluid and replaced more than 3 times per day
57
What is the condition caused by accumulation of CSF? What can this result in and what is the treatment?
Hydrocephalus (water on the brain)
Brain damage if left untreated
Treatment is a shunt to move CSF to veins elsewhere in the body
58
What are the 2 mechanisms constituting the blood brain barrier?
Transport between the wall-forming cells is anatomically prevented
Transport through the cells is physiologically restricted
59
How is transport between cells anatomically prevented in the blood brain barrier?
• Tight junctions seal endothelial cells of brain capillaries
o Prevents passage of plasma components moving between cells
o All possible exchanges must occur through a cell
• Astrocyte processes press up against capillaries
o Secrete chemical that maintain strength in tight junctions
60
How is transport through the cells physiologically restricted in the blood brain barrier?
• Facilitated transport completed by highly selective membrane bound carriers ensure strict limitations of ions, amino acids, and glucose
o Increase in K+ in blood does not result in increase in K+ in CSF
Ensures proper chemical needs for nerve impulses
• Proteins and most antibiotics cannot enter
• Prevents hormones from entering as they may act as neurotransmitters from reaching the brain producing uncontrolled nervous activity
61
What substances easily pass through the blood brain barrier?
• Lipid soluble substances diffuse easily
o Oxygen
o Carbon dioxide
o Steroid hormones
o Alcohol
• Water passes between phospholipid molecules of the plasma membrane
62
What are circumventricular organs?
* Certain areas of the brain not subject to the blood brain barrier
* Capillaries not sealed by tight junctions
* Allows organs to sample blood and adjust output maintaining homeostasis
* Includes capillaries available for hormones to be released into
63
When can the blood brain barrier provide a roadblock for doctors?
Limits use of drugs for treatment of brain and spinal cord disorders because many drugs are unable to penetrate the barrier
64
What is a protein in the brain that may be an oxygen carrying protein?
Neuroglobin
65
Describe anaerobic metabolism in the brain
The brain is unable to produce ATP in anaerobic conditions
66
How long before brain damage begins to occur if the glucose supply is cut off? Why is this?
About 15 minutes. Brain uses nearly exclusively glucose for energy production and does not store any in the brain
67
Describe the names of the pairs of nerves emerging from the spinal column?
```
o 8 pairs of cervical (C1 – C8)
First pair between atlas and occipital bone
o 12 pairs of thoracic nerves (T1 – T12)
o 5 pairs of lumbar nerves (L1 – L6)
o 5 pairs of sacral nerves (S1 – S5)
o 1 pair of coccygeal nerves (Co1)
```
68
What is the thick bundle of elongated nerve roots within the lower vertebral canal?
Cauda equina
69
Describe the cauda equina
* Wispy roots of lower spinal nerves that angle inferiorly with the filum terminale
* Made of nerves of the lumbar, sacral, and coccygeal regions of the spinal column
* Spinal cord ends about L1 or L2 before these nerves leave the column
* Site of spinal tap as no risk of penetrating spinal cord
70
Describe the grey and white matter appearance of the spinal cord?
Grey matter forming an inner butterfly-shaped region surrounded by the outer white matter
71
What does the grey matter of the spinal cord consist of?
cell bodies with dendrites, short interneurons, and glial cells
72
Describe the white matter of the spinal cord
* Act as highways for nerve impulse propagation
| * Tracts are bundles of axons with similar functions
73
What are the 2 types of tracts in the spinal cords white matter?
Ascending and descending tracts
74
Describe the ascending tracts in the white matter of the spinal column?
o Sensory tracts
Conduct nerve impulses from spinal cord to brain
Become thicker as they go up
75
Describe the descending tracts in the white matter of the spinal column?
o Motor tracts
Conduct nerve impulses from brain down spinal cord
Become thinner as they go down
76
Describe the ventral (anterior) and posterior (dorsal) spinocerebellar tract?
Ascending pathway
Originates in spinal cord, runs up ventral margin with several synapses along the way and terminates in the cerebellum
Carries information from muscle stretch receptors
77
Describe the ventral (anterior) and lateral corticospinal tract?
Descending pathway
Originates in the motor region of the cerebral cortex, travels down ventral portion of spinal cord, and terminates in spinal cord on cell bodies of efferent motor neurons supplying skeletal muscles
78
Describe the anterior and lateral spinothalamic tracts
* Ascending tract
* Located in anterior white funiculus
* Begins in spinal cord and ends in thalamus
* Convey pain, itching, tickling, deep pressure, and thermal sensations
79
Describe the posterior funiculi
• Ascending tract
• Composed of gracile fasciculus and cuneate fasciculus
• Carry impulses for
o Proprioception
o Discriminative touch (ability to feel what part of body is touched)
o Two-point discrimination (ability to distinguish touching of two different points of skin, even though they are close together)
o Light pressure sensation
o Vibration sensation
80
Where is CSF located in the grey matter of the spinal cord?
Inside the central canal which lies in the center of the grey matter
81
What are the divisions of the grey matter of the spinal cord and what doe each contain?
Anterior (Ventral) Gray Horn
• Contains somatic motor nuclei
• Provide nerve impulses for contraction of skeletal muscles
Posterior (Dorsal) Gray Horn
• Contains cell bodies of and axons of interneurons
• Contains axons of incoming sensory neurons
Lateral Gray Horns
• Only present in thoracic, upper lumbar, and mid-sacral segments
• Contain cell bodies of autonomic motor nuclei
o Regulate smooth and cardiac muscle
o Regulate glands
82
What are nuclei in the CNS?
• Clusters of neuronal bodies that form functional groups
83
Describe the anterior (ventral) roots
* Formed by convergence of each series of anterior rootlets
* Contain efferent fibers sending signals to muscles and glands
* Cell bodies for efferent neurons exist in grey matter and axons exit with the ventral root
84
Describe posterior (dorsal) roots
• Formed by convergence of each series of posterior rootlets
• Dorsal root ganglion
o Swelling on each posterior root
o Contains cell bodies of sensory (afferent) neurons
85
Describe spinal nerves
* Mixed nerve that contains both motor and sensory axons
* Formed by the convergence of the sensory posterior root and motor anterior root as they head laterally from the spinal cord
* Enclosed by a covering of connective tissue
* Individual fibers have no direct influence on each other, just travelling together for convenience as they are going to the same general area
* Only goes a short distance before branching
86
How many spinal and cranial nerves make up the peripheral nervous system?
31 spinal and 12 cranial nerves
87
What is a dermatome?
* Specific region of the body surface supplied by a particular spinal nerve
* These nerves also carry fibers going to internal organs
88
What is referred pain?
* Pain originating from one of the organs is referred to the corresponding dermatome supplied by the same spinal nerve
* Mechanism not completely understood
89
What is a reflex?
* Fast, involuntary, unplanned sequence of actions that occurs in response to a particular stimulus
* Evolved to protect an individual faster than cognition allows
* Some are instinctive, some are learned (like slamming on the brakes)
90
What are built-in, unlearned reflex responses called?
Simple (basic) reflex
91
What are acquired reflexes?
Also called conditioned reflexes
• Result of practice and learning
• Originally takes considerable conscious effort
• An example is reading music and playing automatically
92
What is a reflex arc and how does it work?
• Neural pathway involved in accomplishing reflex activity
• Sensory receptor responds to a stimulus
• Impulse conducts down sensory neuron axon
• Impulse reaches integration center in the grey matter
o Brain for acquired reflexes
o Spinal cord for basic reflexes
• Impulse sent to a motor neuron that will respond
o Occurs in either the brain or spinal cord depending on the integration center
• Effector muscle or gland is reached and contracts or secretes
• At the same time the motor neuron is triggered relay neurons send impulses to the brain
93
What are funiculi?
• 3 broad areas of white matter divided by the gray horns
o Anterior (ventral) funiculus
o Posterior (dorsal) funiculus
o Lateral funiculus
• Each contains distinct bundles of axons having a common origin or destination and carrying similar information
94
Describe the rubrospinal tract in the spinal column
Descending tract
| Provides involuntary control of skeletal muscles for tone and posture
95
Describe the vestibulospinal tract of the spinal column?
Descending tract
| Involuntary control of balance and equilibrium
96
What is a reflex that involves only 1 synapse called?
Monosynaptic reflex
97
What is a reflex that involves multiple synapses called?
Polysynaptic reflexes
98
What test is routinely used to test nervous system function and what does it show?
```
Patellar tendon reflex
o Tests many components
Muscle spindle
Afferent input
Motor neurons
Efferent output
Neuromuscular junctions
Muscle contraction
o May be absent or depressed with loss of higher-level excitatory inputs
o May be exaggerated with loss of inhibitory input to the motor neurons from higher brain levels
```
99
How does the patellar tendon reflex work and what is its primary purpose?
* Tapping on the patellar tendon stretches the quadriceps muscle, stretching spindle fibers and activating their receptors
* Causes contraction of the extensor muscle causing the knee to extend and raise the lower leg
* Primary purpose is to prevent the knees from buckling under pressure of gravity
100
What are spinal reflexes?
* Integration that takes place in the gray matter of the spinal cord
* The spinal reflex acts immediately to prevent injury
* Other interneurons carry the signal to the brain for conscious interpretation
* Ex is patellar reflex and withdraw reflex
101
What is reciprocal innervation?
* Neuronal connection involving stimulation of one muscle and simultaneous inhibition of nerves to its antagonistic muscle
* An example is the withdraw reflex where the biceps is excited, and triceps is inhibited to allow pulling the hand away from something hot/painful
102
How does someone voluntarily override a withdraw reflex?
* Used when you are aware the painful stimulus is coming but must remain still
* Brain sends more IPSPs to the bicep than it receives EPSPs from the stimulus
* Brain sends more EPSPs to the triceps than it receives IPSPs from the stimulus
* Results in arm staying still and not withdrawing
103
What is the Babinski ankle jerk reflex and what conditions is it associated with?
• Infantile reflex normal until 2 years
• After age 2 its an indication of corticospinal tract issues
• Common associated diseases are
o Amyotrophic lateral sclerosis
o Head injury
o Meningitis
o Multiple sclerosis
o Spinal cord injury
o Stroke
o Tuberculosis
o Rabies
• Sole of foot is stimulated by a sweeping pressure
• Positive when the big toe dorsiflexes (straightens) and the other toes fan outward
• Negative when toes curl towards sole of the foot
104
What is a crossed extensor reflex?
* Simple postural reflex
* Stimulates the leg opposite the one that has been received the stimuli
* Allows you to put weight onto your good leg after you accidentally step on a tac
105
What are the 5 main functions of the brain stem?
All but the 12 pairs of cranial nerves arise from brain stem
Contains centers for cardiovascular, respiratory, and digestive functions
Regulating reflexes for equilibrium and posture
Contains reticular formation forming the reticular activating system
May help with sleep
106
What is the reticular formaiton?
• Netlike arrangement of small clusters of neuronal cell bodies (gray matter) interspersed among small bundles of myelinated axons (white matter)
• Extends from spinal cord to inferior diencephalon
These fibers compose the reticular activating system
107
Describe the reticular activating system
• Ascending (sensory) functions
• Sensory axons projecting into cerebral cortex, both directly and through thalamus
• Responsible for
o Consciousness
o Arousal, or waking up
o Attention and alertness
o Auditory and visual stimuli
o Mental activities
o Stimuli from pain, touch, pressure, and proprioceptors
• Prevents overload by ignoring unimportant stimuli
• Inactivation leads to sleep
o Melatonin and general anesthesia work here
• Damage results in coma
108
What are the descending motor functions of the reticular formation?
* Regulates muscle tone
| * Assists in regulation of heart rate, blood pressure, and respiratory rate
109
What are the 12 cranial nerves?
```
1 - olfactory
2 - optic
3 - oculomotor
4 - trochlear
5 - trigeminal
6 - abducens
7 - facial
8 - vestibulocochlear
9 - glossopharyngeal
10 - vagus
11 - accessory
12 - hypoglossal
```
110
Describe cranial nerve 1
Olfactory (I) Nerve
• Entirely sensory for olfaction
• Olfactory epithelium line superior part of nasal cavity, covering inferior surface of cribriform plate and extending down along the superior nasal concha
• Are bipolar neurons
• Bundles of axons extend into 20 olfactory foramina of cribriform plate of ethmoid bone which collect into right and left olfactory nerves
111
Describe cranial nerve 2
Optic (II) Nerve
• Entirely sensory for vision
• Technically a tract of brain and not a nerve
• Rods and cones initiate visual signals and relay them to bipolar cells and then transmitted to ganglion cells
• Axons of ganglion cells join to form an optic nerve passing through optic foramen
112
Describe cranial nerve 3
Oculomotor (III) Nerve
• Originates from motor nucleus in anterior part of midbrain
• Extends anteriorly and then divides into a superior and inferior branch both passing through superior orbital fissure into orbit
• Superior branch innervates
o Superior rectus muscle
o Levator palpebrae superioris muscle (muscle of upper eyelid)
• Inferior branch innervates
o Medial rectus muscle
o Inferior rectus muscle
o Inferior oblique muscle
o Parasympathetic motor axons to
Ciliary muscle of eyeball causing adjustment of lens for near vision
Circular muscles (sphincter pupillae) of iris causing constriction
113
Describe cranial nerve 4
Trochlear (IV) Nerve
• Originates from trochlear nucleus in midbrain
• Arises from posterior aspect of brainstem, goes around pons, and exits superior orbital fissure into the orbit
• Innervates superior oblique muscle of eyeball
114
Describe cranial nerve 6
Abducens (VI) Nerve
• Originates from abducens nucleus in pons
• Extends anteriorly through superior orbital fissure into orbit
• Innervates lateral rectus muscle
115
Describe cranial nerve 5
Trigeminal (V) Nerve
• Named because of the 3 branches - ophthalmic, maxillary, and mandibular
• Has 2 roots on the anterolateral surface of the pons
o Large sensory root
o Smaller motor root originates in a nucleus in pons
• Sensory ganglion located in the temporal bone
o Sensory axons carry impulses for touch, pain, and thermal sensations
o Axons terminate in nuclei of pons
• Contains sensory axons from proprioceptors located in muscles of mastication and extraocular muscles
116
Describe cranial nerve 7
Facial (VII) Nerve
• Sensory axons extend from taste buds of anterior 2/3 of tongue passing into the geniculate ganglion to the pons, then to the thalamus, and finally to the gustatory areas
• Contains sensory information from skin in external acoustic meatus about touch, pain, and thermal sensations
• Contains proprioceptors from muscles of face and scalp
• Motor neurons arise in nucleus of the pons and innervate
o Middle ear
o Facial, scalp, and neck muscles allowing for facial expression
• Parasympathetic motor neurons extending to facial glands
117
Describe cranial nerve 8
Vestibulocochlear (VIII) Nerve
• Sensory cranial nerve
Vestibular Branch
• carries impulses for equilibrium
• Extends to vestibular nuclei in pons and cerebellum
Cochlear Branch
• Carries impulses for hearing
• Extends to cochlear nuclei in medulla oblongata and ending in thalamus
118
Describe cranial nerve 9
Glossopharyngeal (IX) Nerve
• Sensory axons arise from
o Taste buds on posterior 1/3 of tongue
o Proprioceptors from swallowing muscles
o Baroreceptors in carotid sinus
o Chemoreceptors in carotid and aortic bodies
o External ear regarding touch, pain, and thermal sensations
• The sensory axons pass through jugular foramen and end in medulla
• Motor neurons arise in nuclei of medulla and exit through jugular foramen
o Innervates stylopharyngeus muscle assisting in swallowing
• Axons of parasympathetic motor neurons stimulate parotid gland to secrete saliva
119
Describe cranial nerve 10
Vagus (X) Nerve
• Sensory axons arise from
o Skin of external ear for touch, pain, and thermal sensations
o Few taste buds in epiglottis and pharynx
o Proprioceptors in muscles of neck and throat
o Baroreceptors in carotid sinus
o Chemoreceptors in carotid and aortic bodies
o Visceral sensory receptors in most organs of thoracic and abdominal cavities
Sensations include hunger, fullness, discomfort
• Motor neurons arise from nuclei in medulla
o Supply muscles of pharynx, larynx, and soft palate
o Used for swallowing, vocalization, and coughing
• Parasympathetic motor axons
o Initiate contractions in digestive canal to aid in motility
o Stimulates secretion of digestive glands
o Activates smooth muscle to constrict respiratory passageways
o Decreases heart rate
120
Describe cranial nerve 11
Accessory (XI) Nerve
• Also called a spinal accessory nerve
• Arise from cervical spine, exit laterally, go up through foramen magnum, and then back out through the jugular foramen
• Conveys motor impulses for sternocleidomastoid and trapezius muscles to coordinate head movements
• Sensory nerves from proprioceptors in sternocleidomastoid and trapezius muscles start with accessory nerve but leave to join the cervical plexus while others remain with accessory nerve
121
Describe cranial nerve 12
Hypoglossal (XII) Nerve
• Motor cranial nerve supplying the muscles of the tongue
• Originate in hypoglossal nucleus in medulla, exiting the anterior surface
• Allows for speech and swallowing
• Proprioceptors that begin with this nerve leave to joint the cervical spinal nerves
122
Describe the diencephalon
* Located between cerebrum and midbrain
* Surrounds the third ventricle
* Consists of the thalamus, hypothalamus, and epithalamus
123
Describe the thalamus
* Consist of paired oval masses of gray matter organized into nuclei with interspersed tracts of white matter
* Interthalamic adhesion joins the right and left sides
* Relay center for impulses (except smell)
* Directs sensory impulses to specific areas of the brain for interpretation
* Responsible for cocktail party effect
* Reinforces voluntary motor signals from cortex
124
Describe the functions of the hypothalmus
• Control and integration of autonomic nervous system
o Axons extend to sympathetic and parasympathetic nuclei in brainstem and spinal cord
o Major regulator of visceral activities
• Production of hormones
o Connections to anterior pituitary through median eminence of intermediate area
o Connections to posterior pituitary through infundibular stalk of intermediate area
These neurons make oxytocin and antidiuretic hormone
• Works with limbic system for regulation of emotional and behavioural patterns
• Regulates food intake, thirst, and urine production
• Controls body temperature
• Regulation of circadian rhythm through suprachiasmatic nucleus in anterior area
• Controls uterine contractions and milk ejection
125
What is the hypothalamus?
* Means under the thalamus
* Vital link between autonomic nervous system and endocrine system
* Primarily serves to regulate the internal environment
126
Describe the cerebrum
• Also referred to as the telencephalon
• Most activity happens here
o Higher functioning, reasoning, memory, intelligence etc.
o Voluntary motor actions and sensory processing
• Split into 2 hemispheres
o Left
More active during speech
Controls right side of the body and the right side of both eyes
o Right
Controls the left side of the body and the left side of both eyes
127
What separates and connects the left and right hemispheres of the cerebrum?
o Separated by longitudinal cerebral fissure
o Connected via corpus callosum at the floor of the longitudinal fissure
A tract of white matter
Allows for information sharing
128
What is the cerebral cortex and what is it composed of?
* Surface of the cerebrum is cerebral cortex and made of grey matter
* Consists mostly of densely packed neuronal cell bodies, their dendrites, and glial cells
129
Describe the white matter of the cerebrum. Why is it white?
* Located deep to the cortex
* Primarily myelinated axons in tracts
* White due to the lipid composition of the myelin
130
What is the region of grey matter located deep within the white matter called?
Basal ganglia
131
During a stroke, why are more than just the oxygen deprived cells die?
* Initial cell death is a result of oxygen deprivation (necrosis)
* Oxygen starved cells release excess glutamate causing excess K+ to be taken into the neurons, triggering apoptosis
* K+ diffuses through gap junctions, triggering apoptosis in even more originally undamaged neurons
132
Describe the layers of the cerebral cortex as well as the 2 important specialized cells found here
* 6 layers that extend perpendicularly about 2mm from the cortical surface down to the white matter
* All neurons in a given column function as a team
* Functional differences result from different layering patterns and input-output, not specialized cell types
Stellate Cells
• Responsible for initial processing of sensory input to cortex
• More located in areas of brain responsible for sense perception
Pyramidal Cells
• Send fibers down the spinal cord and terminate on efferent motor neurons for skeletal muscle
• More located in areas that control skeletal muscle
133
What is the deep fold that separate the frontal and parietal lobes?
Central sulcus
134
Describe the location and function of the primary motor cortex. Describe the specialized Betz cells located here.
• Located in precentral gyrus, immediately anterior to the central sulcus, of frontal lobe
• Controls voluntary muscle contraction for the opposite side of the body
• Takes speech information from Broca’s area and coordinates it with breathing
• Betz cells
o Large pyramidal cell neurons with long axons
o Descend through spinal cord
o Synapse with alpha motor neurons of skeletal muscles
Neurotransmitter is glutamate
135
Describe the location and function of the premotor cortex
• Located on the lateral surface of each hemisphere anterior of the primary motor cortex
• Works with basal ganglia to plan simultaneous or sequential muscle contractions so movements are coordinated
• Important in orienting the body towards a target
• Receives sensory input from
o Cerebellum to refine movements
o Posterior parietal cortex
• Serves as a memory bank for such coordinated movements
136
Describe the motor tracts that may be taken from the motor cortex to the muscles of the body
* Some cross over at the medulla and descend the lateral corticospinal tract
* Some travel down the same side in the ventral corticospinal tract and cross over just before reaching the motor neuron
137
What is a homunculus?
Depicts location and relative amount of motor cortex devoted to the output of muscles for each body part
138
Describe the difference between the homunculus and the neural network beneath
The superficial homunculus structure if fairly stable.
| Neuronal patterns is plastic and is activity dependent allowing us to modify the pathways when learning new skills
139
Describe the primary somatosensory cortex location and function
• Directly posterior to central cerebral sulcus in postcentral gyrus of each parietal lobe
• Primary sensory areas are often adjacent to secondary sensory areas and association areas
• Receives information
o Somaesthetic sensation
Body feelings including touch, pressure, heat, cold, pain, itch, and tickle
o Proprioception
Joint and muscle position
• Sends information to other parts of the brain for further interpretation via white matter tracts
140
Describe the cerebellums role in voluntary muscle movement
• Subcortical region that plays a role in sending the input to motor areas of the cortex regarding planning, initiating, and timing
141
What are the higher motor areas and what is their function?
Supplementary motor area, premotor cortex, and posterior parietal cortex
• Provide the coordination required to accomplish desired complex movement
o Works with the cerebellum to achieve this
142
What is readiness potential?
o Widespread pattern of neuronal discharge that occurs 750 milliseconds before any activity is detected in the motor cortex
o The delay is due to the decision-making process in higher motor areas
143
Describe the location and function of the supplementary motor area?
* Located on the medial surface of each hemisphere anterior of the primary motor cortex
* Prepares for complex sequences of movement
* Lesions result in alteration in performance of more complex, useful, integrated movements
144
Describe the location and function of the posterior parietal cortex
* Located just posterior to the somatosensory cortex
| * Provides information about where the body is in relation to the target
145
Describe somatotopic maps and how it is developed in the individual
• Basic organization is the same from person to person
• Precise distribution is unique for each individual
• Mapping governed by genetic and development process and is plastic
• Influenced by use-dependent competition, only so much room, so what is used more takes up more space, this is also plastic
• Localization of sensation is made of
o Somatotopic stage
Identifying stimulus location relative to its position on the skin
o Deciding limb position in external space
146
Describe plasticity and neurogenesis
* Not entirely understood
* Dendrites change shape making new connections without making new neurons
* Neurogenesis recently proposed to develop new neurons as treatments for disorders or damage
147
Describe an EEG as well as its uses
• Record of brain waves that are generated by neurons close to brain surface
o Brain waves represent momentary collective postsynaptic potential activity
• Electrodes placed on the forehead and scalp detect the waves
• Useful in study of
o Normal brain functions
I.e. changes during sleep
o Diagnosis of brain disorders
Epilepsy
Tumors
Metabolic abnormalities
Sites of trauma
Degenerative diseases
• Determine various stages of sleep
• Used to establish or confirm occurrence of brain death
148
Describe the functional regions of the cerebellum and their roles
Vestibulocerebellum
• Maintains balance
• Controls eye movement
Spinocerebellum
• Enhances muscle tone
• Coordinates skilled, voluntary movement
• Manages timing of muscle contractions involving moving multiple joints
• Receives information from proprioceptors
• Compares intentions with actual performance and corrects any deviations
• Allows for rapidly changing activities like typing
Cerebrocerebellum
• Plans and initiates voluntary activity and provides input to motor areas
• Stores procedural memories
149
What is the main function of the basal ganglia in relation to movement?
Provides inhibitory inputs to ensure there is no unwanted movements and to prevent any over tension in the posture muscles
150
What is the most common disease of the basal ganglia?
Parkinsons
151
Which part of the limbic system is responsible for fear?
Amygdala
152
Describe the limbic system
* Also called the emotional brain
* Is involved in a range of emotions as well as smell and memory
* Encircles the upper part of the brainstem and corpus callosum
* Ring of structures on the inner border of cerebrum and floor of diensephalon
153
What is memory trace?
The neural change responsible for retention or storage of knowledge
We store concepts not words
154
How long is short term memory?
Seconds to hours
155
How long is long-term memory?
days to years
156
What is the process called when moving information from short-term memory to long-term memory?
Consolidation
157
What is the concept of working memory?
The blackboard of the mind - temporarily holds various pieces of information required for the current task
Helps string thoughts together logically and plan for future action
158
How does the hippocampus play a role in memory?
• Integrates related stimuli for short term memory
• Plays role in consolidation into long-term memory
• Declarative memory
o Record of episodic events
o Works with other regions to maintain this memory
159
What is working memory and where is it stored?
The ability to hold and manipulate information in the short term
Located in prefrontal cortex
160
What is the mechanism for short term memory?
Transient modifications in function of pre-existing synapses
161
What is the mechanism for long-term memory?
Relatively permanent functional or structural changes between existing neurons in the brain
162
What causes short term memory? Describe the 2 forms of short term memory?
Due to modification of different channel proteins in presynaptic terminals of specific afferent neurons involved in the pathway that mediates the behavior being modified
Habituation - decreased responsiveness to repetitive presentations of an indifferent stimulus
K+ channels closed, reducing K+ entry into cell, which reduces neurotransmitter release
Allows for attention to focus on more important stimuli
Sensitization - increased responsiveness to mild stimuli following a strong or noxious stimulus
Increased K+ entry into cell, increases neurotransmitter release, increasing response
163
What does long term potentiation mean?
Prolonged increase in strength of existing synaptic connections in activated pathways following brief periods of repetitive stimulation
Can last for days or weeks to consolidate memory to long term
164
What is believed to ensure that only important information is saved and not everything that an individual encounters?
A balance between positive factors (controlled by CREB protein) and repressive factors (controlled by CREB2 protein)
165
Describe Broca's area
• Located in frontal lobe close lateral to the cerebral sulcus generally on the left
• Responsible for planning and production of speech
• Damage causes inability to form words
o Called non-fluent aphasia
166
Describe Wernicke's area
• Broad region in left temporal and parietal lobes
• Interprets meaning of speech by recognizing spoken words
• Works with auditory input to hear words, visual to see words, and touch receptors for Braille to comprehend language
• Damage causes inability to arrange words in coherent fashion
o Called fluent aphasia
o Also called word salad
167
Describe the prefrontal association cortex
```
• Located anterior to the premotor cortex
• Responsible for
o Planning voluntary activity
o Decision making
o Creativity
o Personality traits
```
168
Describe the Parietal-Temporal-Occipital Association Cortex
```
• Allows for formation of thoughts based on multiple sensory inputs
• Bordered by somatosensory, visual, and auditory association areas
• Receives information from
o Somatosensory association area
o Visual association area
o Auditory association area
o Gustatory cortex
o Olfactory cortex
o Thalamus
o Parts of brainstem
```
169
What is consciousness?
The subjective awareness of the external world and self
170
What are the 4 states of consciousness?
Maximum alertness
Wakefulness
Sleep
Coma
171
What does maximum alertness depend on?
Attention-getting sensory input that stimulates the reticular activating system and subsequently the activity level of the CNS as a whole
172
What is a coma and what may cause it?
Total unresponsiveness to external stimuli
| Brain stem damage that interferes with the RAS or by widespread depression of the cerebral cortex
173
What is the sleep-wake cycle?
Normal cyclic variation in awareness of surroundings
174
What are the two types of sleep?
Slow-wave sleep - delta-wave or non-REM sleep
| Paradoxical sleep - REM sleep
175
Describe the average sleep cycle
4 stages of slow wave sleep, each progressively lower frequency and higher amplitude, which takes about 45 min; reverse through the stages in the same amount of time; then about 10-15 min in REM sleep at the end of each cycle
176
What does an EEG look like during paradoxical REM sleep?
Similar to that of someone that is awake and alert
177
About how much time is spent in REM sleep each night?
20% of sleep time
178
Compare the structure, location, and function of the functional classes of neurons.
Afferent neuron - sensory receptor at peripheral ending, long peripheral axon, cell body devoid of presynaptic inputs located adjacent to the spinal cord, and a short, central axon that terminates in the spinal cord; relays signals from periphery to CNS
Efferent neuron - cell body located in CNS with many presynaptic inputs on it, long peripheral axon that terminates on teh effector organ; carry signals from CNS to effector organs
Interneurons - located entirely in CNS, boy has converging input from afferent and other interneurons, diverging output terminates on efferent neurons or other interneurons; integrate information and formulate response
179
Compare the structure, location, and function of the functional classes of glial cells.
Astrocytes - star-like shape, hold neurons together, support bbb, help repair injuries, and help regulate internal environment
Oligodendrocytes - elongated projections that wrap around axons to form myelin
Microglia - immune cells of CNS
180
Name the meninges from the outermost to the innermost
Dura mater, arachnoid layer, pia mater
181
Explain how the bbb anatomically prevents transport between the cells that form the walls of brain capillaries and physiologically restricts transport through these cells
Anatomically - tight junctions between cells
Physiologically - highly selective membrane carriers
182
Describe the locations of the white and grey matter of the spinal cord
Grey matter looks like a butterfly surrounded by white matter
183
Which side of the spinal cord has the deep groove into the white matter?
ventral side
184
Where does the afferent neuron meet the spinal cord?
Enter the dorsal side of the grey matter
185
Where does the efferent neuron leave the spinal cord?
Through the ventral side of the grey matter
186
Distinguish among a tract, ganglion, nucleus, center, and nerve
A tract is a bundle of nerve fibers (axons of long interneurons) with similar function that travel up (ascending tract) or down (descending tract) in the white matter of the spinal cord
A ganglion is a collection of neuronal cell bodies located outside the CNS
A nucleus, or center, is a functional collection of neuronal cell bodies located within the CNS
A nerve is a bundle of peripheral axons (either afferent or efferent), enclosed by a connective tissue covering and following the same pathway
187
Describe how the thalamus serves as a sensory relay station
All sensory input on its way to the higher cortex synapses in the thalamus, which screens out insignificant signals and routes the important signals to appropriate areas of the cortex. In this way the thalamus serves as a relay station for preliminary processing of sensory input
188
Name the brain area most involved directly in regulating homeostatic functions
Hypothalamus
189
Define plasticity
The ability of the brain to change or be functionally remodeled in response to the demands placed on it
190
State the brain functions associated with the limbic system
Emotions, basic survival and sociosexual behavioral patterns, motivation, and learning
191
Name the brain area most important in processing the sensation of fear
Amygdala
192
Define consolodation
The process of transferring and fixing short-term memory traces into long-term memory stores
193
Compare the molecular mechanisms for short-term and long-term memories
Short-term memory involves transient modifications in the function of pre-existing synapses, such as increased neurotransmitter release from a presynaptic neuron or increased responsiveness of a postsynaptic neuron to neurotransmitter
Long-term memory involves gene activation and protein synthesis that leads to relatively permanent structural or functional changes, such as formation of new synapses
194
Distinguish among declarative memories, procedural memories, and working memory, and indicate the brain area primarily associated with each
Declarative memories are the what memories of specific people, places, objects, facts, and events that often result after only one experiences and the hippocampus is primarily associated
Procedural memories are the how to memories involving motor skills gained through repetitive training and the cerebellum is important here
Working memory temporarily holds currently relevant data - both new information and knowledge retrieved from memory stores - and manipulates and relates them to accomplish complex reasoning functions and the prefrontal association cortex is important here
195
Define consciousness
Consciousness refers to subjective awareness of the external world and self
196
Discuss the location and functions of the three neural systems that play a role in the sleep-wake cycle
1. An arousal system, which is regulated by a group of neurons in the hypothalamus and involves the reticular activating system in the brain stem
2. Slow-wave center in the hypothalamus that contains neurons that induce slow-wave sleep
3. Paradoxical sleep center in the brain stem, which houses REM neurons that switch from slow-wave to REM sleep
197
In a person with a damaged basal ganglia, what would you expect to see?
a) inhibition of muscle tone throughout the body
b) maintenance of purposeful motor activity
c) enhanced coordination of posture and support
d) Parkinson's disease-like symptoms
D
198
What symptom is most likely to occur as the result of a severe blow to the back of the head
visual disturbances
199
Which one of the following would be considered a conditioned reflex?
a) Striking the appropriate letter on a keyboard without looking
b) Removing a body part away from a painful stimulus
c) Swimming
d) Maintaining balance on an uneven sidewalk
A
200
Following a stroke in which an area of the brain is destroyed, which of these statements describes how the lost functions might be recovered?
a) neuronal plasticity
b) stroke damage is always permanent
c) neural regeneration allowing the brain region to re-grow
d) exercise
A
201
When the premotor cortex is damaged, which one of the following will most likely be affected?
a) walking
b) reflexes
c) eating with a fork
d) fine-tuned motor skills
C
202
Hypothesize on the consequences of not having a blood-brain barrier
Without a blood-brain barrier the CSF would be in direct contact with the blood. This would allow changes in blood chemistry or potentially harmful blood-borne substances to have inappropriate influences on the brain
203
The hormone insulin enhances the carrier-mediated transport of glucose into most of the body's cells but not into brain cells. The uptake of glucose from the blood by neurons does not depend on insulin. Knowing the brain's need for a continuous supply of blood-borne glucose, predict the effect that excess insulin would have on the brain
Excess circulating insulin would cause a lowering of blood glucose levels while glucose was moved into the tissues. This would essenti8ally have a starving effect on the brain, which has a need for glucose. Prolonged lack of circulating glucose can lead to neuron death
204
What are some of the potential reasons that a person may not exhibit a patellar tendon reflex?
An intact patellar tendon reflex involves a muscle spindle afferent fiber that projects to the spinal cord and communicates with an alpha motor neuron efferent fiber. A damaged muscle spindle (the sensor) or either impaired afferent or efferent neuron could dampen the reflex
205
Conjecture why the cerebellum is located where it is
Location between occipital lobe and brainstem is essential for integration of sensory input and motor output
206
Sometimes when a person experiences severe trauma they are unable to recall the event. How can this be explained?
A traumatic event such as a concussion or stroke can disrupt the electrical activity of the brain. If a person is knocked unconscious, there is a chance that short-term memory will be erased, leaving the person with no recollection of what has happened. This is commonly called retrograde amnesia.
207
Which division of the central nervous system carries information to the brain?
Afferent
208
Which cell type are the immune cells of the CNS?
Microglia
209
The primary function of the hypothalamus is
a) to be the synaptic integrating center for preliminary processing
b) to be the integrating center for homeostatic functions
c) to regulate muscle reflexes involved in equilibrium and posture
d) to plan and execute movements
B
210
What does Broca's area do?
governs speaking ability
211
What type of EEG sleep pattern resembles that of a wide-awake, alert individual?
REM
212
List the 5 components of a reflex arc
```
Receptor
Afferent pathway
Integrating center
Efferent pathway
Effector
```
213
Describe working memory
Working memory briefly holds and process both newly acquired information and recalls previously stored knowledge in order to evaluate the new data in context
214
Explain the role of the thalamus
The thalamus serves as a synaptic integrating center for preliminary processing of all sensory input on its way to the cortex
215
What is the function of oligodendrocytes
Form the insulating myelin sheaths around axons in the CNS
216
What are somatotopic maps?
General organizational pattern of sensory and motor body representation maps of the cortex
217
Applying your knowledge of the spinal cord, where are the cell bodies of the autonomic efferent fibers?
a) dorsal horn
b) lateral horn
c) ventral horn
d) distal horn
lateral horn
218
Which of the following descriptions is best associated with habituation?
a) K+ channels open to allow K+ entry into presynaptic terminal
b) There is an increase in neurotransmitter release from the presynaptic terminal
c) Repetitive presentations lead to reduced responsiveness
d) There is an increased responsiveness to a mild stimulus following a strong stimulus
C
219
Based on your knowledge of long-term potentiation, which one of the following is a possible cellular pathway?
a) increased AMPA receptors
b) decreased AMPA receptors
c) increased dopamine release
d) decreased dopamine release
A
220
Which part of the brain plans the content of spoken words?
Wernicke's area
221
Using your knowledge of memory, identify the correct brain area important in the consolidation of long-term memories
a) hippocampus
b) basal ganglia
c) cerebellum
d) prefrontal cortex
A
222
Compare and contrast short-term memory with long-term memory
Short-term memory lasts for seconds to hours and has rapid retrieval and limited storage capacity
Long-term memories are retained for days to years, are retrieved slower, and have a very large storage capacity
223
Differentiate between the grey matter and white matter of the spinal cord
Cord grey matter consists primarily of neuronal cell bodies
White matter consists of the axons of long interneurons
224
Distinguish between a monosynaptic and polysynaptic reflex
Monosynaptic reflexes - afferent neuron directly communicates with efferent neuron
Polysynaptic reflexes - interneurons involved in communication between afferent and efferent neurons
225
Explain how cerebrospinal fluid functions as a cushion for the brain
CSF if produced by the choroid plexuses found in particular regions of the ventricle cavities of the brain and flows out to surround both the brain and spinal cord. The density of the CSF is similar to the brain so it is actually suspended in the CSF. Allows the brain to move within the CSF allowing a jarring movement to the head. This motion reduces the intensity of an impact
226
Differentiate between the meningeal membranes
Dura mater - outermost layer that is a tough, inelastic covering
Arachnoid mater - middle layer which is highly vascularized
pia mater - inner layer, highly vascularized and closely adheres to the brain and spinal cord
227
Julio D., who had recently retired, was enjoying an afternoon playing golf when suddenly he experienced a severe headache and dizziness. These symptoms were quickly followed by numbness and partial paralysis on the upper right side of his body, accompanied by an inability to speak. After being rushed to the emergency room, Julio was diagnosed as having suffered a stroke. Given the observed neurologic impairment, what areas of his brain were affected?
Numbness and partial paralysis on the upper right side of the body and inability to speak are indicative of damage to the left somatosensory cortex and left primary motor cortex in the regions devoted to the upper part of the body
The inability to speak is likely caused by damage to Broca's area
