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PHGY 215 > Module 2 > Flashcards

Module 2 Flashcards

1
Q

What are oligodendrocytes?

A

cells in the CNS that produce the myelin sheath surrounding axons

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2
Q

What are interneurons?

A

Cells that play a role in creating neural circuits for integrating responses to peripheral information

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3
Q

What are ependymal cells?

A

Ciliated cells that function to produce cerebrospinal fluid and ensure its flow through the ventricles and central canal of the CNS

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4
Q

What are astrocytes?

A

Form the primary connective tissue to hold neurons in their proper spatial relationships

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5
Q

Describe the function of afferent neurons.

A

Receive info from sensory organs and transmit this input to CNS

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6
Q

What are efferent neurons?

A

Neurons that transmit info from the CNS to muscles and organs

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7
Q

What are activated microglia?

A

Type of immune cell within the CNS that can phagocytose foreign particles, help reduce inflammation, or release cytotoxic chemicals

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8
Q

What are the two main divisions of the peripheral nervous system?

A

Afferent and efferent divisions

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9
Q

Describe the four overarching protective measures for the CNS.

A

bone, protective membranes/meninges, cerebrospinal fluid, blood brain barrier

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10
Q

Describe the components of bone that protect the CNS.

A

cranium/skull surrounds brain, vertebrae of spine surround spinal cord

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11
Q

What are the meninges?

A

three layers of protective membrane called the dura mater (outermost membrane), arachnoid mater(middle membrane), pia mater (innermost membrane)

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12
Q

Describe the Dura Mater.

A

Tough, double membrane with its two layers mostly in direct contact

  • separate in certain regions to create dural sinuses or venous sinuses, into which venous blood draining from brain empties to be returned to heart
  • dural sinuses can also have CSF drain into them
  • outermost membrane so next to bone
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13
Q

What is the arachnoid mater?

A

The middle meningeal membrane that is more delicate than the Dura Mater and highly vascularized/provided with vessels especially blood vessels
- in areas of dura sinuses, the projections of this meninges are called arachnoid granulation villi which penetrate through the dura and extend into sinuses, allowing for transfer of CSF from subarachnoid space to cross villi to blood of sinuses

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14
Q

What is the pia mater?

A

innermost meningeal membrane that is highly vascularized, similar to arachnoid mater, and tightly adheres to surface of brain and spinal cord
- dips deeper into brain to bring blood supply to ependymal cells lining ventricles in certain areas

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15
Q

What is cerebrospinal fluid and how does it protect the brain?

A

similar density to brain tissue, allowing brain to be suspended within it, protects brain by acting like a shock absorber

  • located in subarachnoid space and flows through ventricles and Central canal of spinal cord
  • also needed for transfer of material between blood and neural tissues
  • influences the brain’s interstitial fluid (also influenced by blood steam) despite not being in direct contact with it
  • created by choroid plexuses, which are highly vascularized masses of pia mater and dip into pockets of ependymal cells to create CSF and are found in each of four ventricles
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16
Q

What is the purpose of the blood brain barrier?

A

ensure sudden changes in blood plasma composition won’t influence composition of brain’s interstitial fluid and affect neuronal function

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17
Q

What forms the blood brain barrier?

A

endothelial cells of brain capillaries are joined together by tight junctions to prevent materials from passing between cells
- this means exchange of materials between blood and brain must pass through endothelial cells so insures high regulation

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18
Q

What is the spinal cord?

A

A long tube of neurons and support cells that extends from the brain stem through a hole in the skull to the lumbar region of the vertebral column

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19
Q

Describe the function of the spinal cord.

A

conducts the flow of info between the brain and body and has the ability to independently control reflexes

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20
Q

Describe the levels of protection provided to the spinal cord.

A

it is encapsulated by meninges creating an extracellular environment unique from the rest of the body
- additionally, vertebrae provide physical protection

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21
Q

What are the differences between the grey matter of the spinal cord and the white matter of the spinal cord?

A

Grey matter: consists of nerve cell bodies, short interneurons, and glial cells

  • contains the central canal filled with CSF
  • contains horns which are regions of grey matter the different cell bodies they contain

White matter: consists of bundles of nerve fibres or axons, with each panel connected to specific region of brain to transmit info

  • descending tracks of efferent neurons transmit info from brain to periphery
  • ascending tracks of afferent neurons transmit info from periphery to brain
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22
Q

Describe the differences between the dorsal horn, lateral horn, and ventral horn of the spinal cord’s grey matter.

A

dorsal horn: interneuron cell bodies on which afferent neurons terminate

lateral horn: cell bodies of autonomic efferent nerve fibres

ventral horn: cell bodies of somatic efferent neurons

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23
Q

what is the dorsal root ganglia?

A

located outside of spinal cord, contain cell bodies of afferent nerves
- connected to spinal cord by two different pathways, the dorsal root containing afferent input and the ventral root containing efferent input

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24
Q

where are efferent cell bodies located?

A

Within the spinal cord, unlike afferent cell bodies

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25
Q

What is the role of afferent nerve cell bodies (which are located in the dorsal root ganglia outside of the spinal cord)?

A

receive info from periphery and relay to interneurons of dorsal horn within spinal cord gray matter

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26
Q

Describe the structure of a nerve.

A

bundle of peripheral afferent and efferent axons that are following same pathway

  • covered in connective tissues
  • note: axons share same pathway but they are not communicating with each other
  • nerves do not contain cell bodies of neurons, only axons, as cell bodies of neurons are found within CNS or ganglia in PNS
  • contain nerve fascicles
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27
Q

what are nerve fascicles?

A

bundles of myelinated or unmyelinated axons in connective tissue and blood vessels
- contained within nerves

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28
Q

explain the structure of the spinal cord.

A

along the vertebral column, pairs of spinal nerves project from between vertebrae and are named according to regions they innervate (meaning to synapse with another tissue)

  • cervical cord has 8 pairs
  • thoracic cord has 12 pairs
  • lumbar cord has 5 pairs
  • sacral cord has 5 pairs
  • final spinal nerve pair is coccygeal nerve
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29
Q

describe the two types of spinal reflexes.

A

simple reflexes: unlearned responses

acquired reflexes: result of practice, training, conditioning

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30
Q

what is a stretch reflex?

A

associated with skeletal muscles which contains stretch receptors that are activated when muscle is stretched

  • when stretch receptors are activated, afferent fibre ends directly on efferent neuron so communicates without interneuron
  • in turn, efferent neuron supplying same muscle is activated and causes the muscle to contract
  • acts as negative feedback mechanism that resists passive change in muscle length
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31
Q

what is a withdrawal reflex?

A

another type of simple reflex that serves as a protective mechanism for the body
- an example of this is what occurs when touching something hot

32
Q

explain how a reflex arc works.

A

neural pathways for reflexes with five basic components that are the same for all unconscious reflexes given a particular stimuli

  1. receptors in skin: sense physical or chemical change in environment and produce action potential
  2. afferent neuron: action potential transmitted from receptor to integrating centre
  3. interneuron/integrating center: generally within the CNS (simple reflex is usually generated within spinal cord or brain stem and acquired reflexes processed in higher brain centres), once signal is processed the response is initiated
  4. efferent neuron: transmits response away from CNS
  5. effector: target of efferent pathway that is usually a muscle or gland and is required to carry out the desired response
33
Q

why is it important for the body to have reflexes independent from the brain’s direction?

A

entire reflex arc can be contained within spinal cord and reaction can be initiated even before brain is aware, resulting in rapid choice to keep body safe
- brain can modify or override the reflex but this becomes a conscious decision (for example: when you give a blood sample the same withdrawal reflex is present but your brain is actively overriding inhibitory and excitatory input prior to the painful stimulus)

34
Q

What are the components of the brain stem?

A

midbrain, pons, medulla oblongata

35
Q

describe the midbrain.

A

superior/inferior colliculi, ventral tegmental area (dopamine, motivation and reward), substantia nigra (dopamine, movement)

36
Q

what is the pons?

A

connects medulla and midbrain, contains cranial nerve nuclei

37
Q

describe the medulla oblongata.

A

vital functions, reflexive actions, connected directly to spinal cord

38
Q

List the five major functions of the brain stem.

A
  1. housing cranial nerves
  2. vegetative functions
  3. postural reflexes
  4. reticular activating system
  5. sleep
39
Q

which cranial nerves arise at the level of the brain stem?

A

majority

  • to supply sensory and motor fibres in head and neck
  • nerves originating in brain stem control hearing, eye movement, facial sensations, taste, swallowing, movements of face/neck/shoulder/tongue muscles
40
Q

how does the brain stem control vegetative functions?

A

brainstem contains clusters of neuron/centers that control vegetative functions of cardio, respiratory, digestive systems
- medulla oblongata detects CO2 and O2 levels in blood and determines what changes need to happen, by controlling cardio and respiratory systems

41
Q

why is it important for the brain stem to maintain postural reflexes?

A

posture functions to maintain upright/balanced body position, allowing for a stable background for voluntary activity
- muscle reflexes involved in posture and equilibrium come from the brain stem, equilibrium in this context referring to maintenance of good posture with normal alignment

42
Q

what is the reticular activating system?

A

made up of reticular formation and ascending fibres

  • reticular formation is a network of interconnected neurons which runs throughout brainstem and up into thalamus, and has the purpose of monitoring all incoming sensory input (except smell) and acting as a filter for consciously perceived sensory input
  • ascending fibres originate from reticular formation and pass the selected info along to the cortex
  • descending fibres also exist and terminate at reticular formation, descending from the cortex
43
Q

how does the brain stem function to help us sleep?

A

neurons in the brain stem produce neurotransmitters that act on various parts of brain to control whether we are asleep or awake

  • balance between these sleep promoting and wake promoting neurons determines this
  • GABA is a major inhibitory neurotransmitter and is heavily present during sleep
44
Q

what is the diencephalon?

A

overarching region of brain located in upper end of brain stem, consisting of thalamus, hypothalamus, epithalamus, and subthalamus which all function to relay sensory info between brain regions and control many autonomic functions
- also connects to nervous and endocrine systems to control emotion in conjunction with limbic system

45
Q

describe the location and primary functions of the thalamus.

A

located deep in brain

primary functions: integrating centre for all sensory input on the way to cortex

  • conducts preliminary processing, removing lesser signals so more important ones are sent to appropriate cortical areas
  • can amplify signals of specific interest
46
Q

what does the hypothalamus do?

A

integration centre for homeostatic functions, serving as a link between autonomic nervous system and endocrine system, with many of its functions involving negative feedback
– controls production and/or secretion of pituitary hormones
– plays a role in the sleep–wake cycle
– acts as an autonomic nervous system coordinating centre
– controls uterine contraction and milk ejection
– controls fluid intake
– influences urine output and thirst
– involved in emotion and behaviour
– controls body temperature

47
Q

describe the structure of the cerebral cortex.

A

made of gray matter, which is the area that contains neuron cell bodies with their dendrites and glial cells
– divided into right and left hemispheres which are connected by the corpus callosum
- contains six well defined layers, each made of different cell types, independent but highly interconnected to form cortical microcircuits

48
Q

define corpus callosum.

A

area of brain made of axons, allowing for right and left hemispheres to work together and communicate

49
Q

what are cortical microcircuits?

A

narrow columns through cortex, which allow for functional differences in different areas of cortex

50
Q

what are the frontal lobes?

A

located in front of head and responsible for voluntary motor activity, speech, elaboration of thought
– motor control: contain primary motor cortex

51
Q

describe the primary motor cortex.

A

contains large pyramidal neurons (pyramid shaped, two dendritic trees, primary excitation units of prefrontal cortex)

  • send their axons down spinal cord and synapse with alpha-motor neurons (innervate muscle fibres and cause contraction) of skeletal muscles
  • motor homunculus, which shows relative output of primary motor cortex to different parts of body
  • note: these are not the only brain regions involved in motor control
52
Q

describe the parietal lobes.

A

located between the frontal and occipital lobes

  • primarily responsible for receiving/processing sensory input
  • peripheral nervous system transmits somaesthetic sensations (touch, pressure, cold, hit, pain) to somatosensory cortex
53
Q

what is the somatosensory cortex?

A

located at most anterior region of parietal lobes, initial processing of somaesthetic input as well as proprioceptive input/proprioception occurs here

  • each region of somatosensory cortex receives these two inputs from specific areas of the body
  • unequal representation of body parts in the somatosensory cortex is reflected by the sensory homunculus
  • generally some medicine to record six onone side of brain receives input from opposite side of body, with ascending pathways carrying the sensory info up the spinal cord crossing to the opposite side
  • output received here goes to the higher sensory areas for further processing, analysis and interpretation of sensory input
  • somatosensory cortex is separated from the primary motor cortex by the central sulcus
54
Q

what do proprioceptive input and proprioception mean?

A

sense of where your body parts are and strength of effort employed in movement

55
Q

describe the occipital lobe.

A

located at back of head, initial processing for a visual input

56
Q

describe the temporal lobes.

A

located on side of head, involved in vision and hearing

57
Q

what is the role of the cerebellum?

A

integration of motor control and sensory perception

- no role in voluntary initiation of movement, but contributes to muscle tone, coordination, precision of movement

58
Q

what are the three functionally distinct parts of the cerebellum?

A

vestibulocerebellum: balance, special orientation, control of eye-movement
spinocerebellum: regulates skilled voluntary movements and receives proprioceptive input to allow for continuous fine-tuning of movement
cerebrocerebellum: involved in planning of voluntary movement and evolution of sensory info, receives all of its input from cerebral cortex

59
Q

describe the structure of the basal ganglia.

A

consists of several masses of grey matter, located within cerebral white matter
- four distinct anatomical structures called the caudate nucleus, putamen, globus pallidus, and claustrum

60
Q

describe the functions of the basal ganglia.

A

associated with functions including motor control, cognition, emotions, learning

inhibiting muscle tone throughout body
- normal muscle tone is maintained by balance of excitatory and inhibitory inputs, so adjusting either allows for precise changes in muscle tone

permitting purposeful motor activity
- while suppressing unwanted movements

helping monitor and coordinate sustained contractions
- such as those related to posture

61
Q

why is the basal ganglia are connected to other brain regions, forming a complex feedback loop?

A

due to its critical role in motor control

  • linked to cerebral cortex and thalamus insulin is involved in positively reinforcing voluntary movement initiated by the cortex
  • it can exert inhibitory effect on thalamus and can influence brainstem to inhibit motor activity as well
62
Q

what are the brain regions associated with the limbic system? why these specific regions?

A

lobes of cerebral cortex (temporal and frontal), cingulate gyrus, fornix, basal ganglia, thalamus, hippocampus, amygdala, hypothalamus, olfactory bulb

these regions are associated with emotions, behavior, motivation, learning, and interconnected by neural pathways

63
Q

what are the primary functions of the limbic system?

A

emotions, forming memories

64
Q

what is behavior and which structures of the limbic system are involved in it?

A

behaviour is a broad range of actions or mannerisms made by individuals as they interact with their environments and is characterized by responses to various stimuli and inputs
- can be conscious or unconscious, voluntary or involuntary

experimental simulation of the limbic system has shown it can elicit a wide range of complex behaviours
- hypothalamus, which governs involuntary internal responses in preparation for appropriate action
- cerebral cortex, which provides neural mechanisms necessary for regulating skeletal muscle responses needed for behaviours
(higher cortical areas can also modify, reinforce, or suppress behavioural responses to permit more refined responses that are based on the analysis of current situation or a previous experience)

65
Q

what is motivation? how can it be homeostatic? and how does it involve the brain’s reward circuit?

A
  • ability to direct behaviour towards specific goals
  • some motivated behaviours are homeostatic in nature (for example, if body has a water deficit, there’s a homeostatic drive for kidneys to conserve water and thirst is initiated)
  • behaviours that have previously proven to be gratifying may motivate repetition of said behaviors, and the opposite is true of punishment centres associated with a certain behaviour (some behaviours are repeated despite activation of punishment centres because ultimately it leads to a long-term reward)
66
Q

define learning.

A

acquisition, modifying, reinforcing of knowledge or skills based on experience/instruction
- process, so generally doesn’t occur with one event and gradually builds on previous experiences, can change over time

67
Q

compare and contrast punishment and reinforcement.

A

both are major influences on learning and can be positive (addition of something) or negative (removal of something)
- reinforcement for a behaviour increases the likelihood of repeating the behavior, while punishment associated with a behaviour is likely to suppress the behaviour

68
Q

define the types of punishment and reinforcement (in terms of positive and negative).

A

positive punishment: adding something to decrease behaviour

positive reinforcement: adding something to increase behaviour

negative punishment: subtracting something to decrease behaviour

negative reinforcement: subtracting something to increase behaviour

69
Q

define memory.

A

Storage of acquired knowledge for later recall

  • it’s not possible to learn without memory
  • takes place in the form of neural networks
  • forms the basis by which individuals can change behaviour (along with learning)
70
Q

what are memory traces?

A

also known as engrams, these are hypothetical storage forms of permanent neural changes in the nervous system caused by learning

  • generally, conceptual and reinforced with learning, but can also be specific like memorizing text word-for-word
  • not stored within a single neuron, and is actually a pattern of signals transmitted across synapses in a wide network
71
Q

how is memory acquired?

A

occurs in multiple stages, starting with newly acquired info stored in short-term memory, which has a limited storage capacity

  • once in short-term memory, info now has two paths
  • it is either forgotten or transferred to long-term memory through practice and rehearsal (more often new knowledge is recycled in short term memory, more likely it is to be transferred to long-term memory, which has a large storage capacity)
72
Q

which parts of the brain are involved in memory trace storage?

A

neurons involved in memory traces which are widely distributed throughout the hippocampus, limbic system, cerebellum, prefrontal cortex, and other regions of the cerebral cortex

  • hippocampus: vital role in short-term memory and consolidation and also stores long-term memories before they are transferred to other critical sites for more permanent storage (also contains decorated memories or the white memories of specific people, places, effects etc.)
  • cerebellum: role in procedural memories (or how to memories), which involve motor skills gained through repetitive training and can be recalled without conscious effort
  • prefrontal cortex: complex reasoning skills associated with working memory, and (in cooperation with all of brain’s sensory regions) it’s responsible for executive functions involving integration of info (for planning, juggling priorities, problem-solving, organizing activities)
73
Q

describe the relationship between the Aplysia snail and memory storage.

A

used to study the different kinds of short term memory, it is easier to work out their neural pathways as compared to humans since they have 15,000-20,000 compared to 100 billion
- Aplysia brain allowed discovery/demo of two forms of short-term memory: habituation and sensitization

74
Q

explain habituation.

A

decreased responsiveness to repetitive presentations of indifferent stimulus that neither rewards nor punishes
- depresses synaptic activity

75
Q

what does sensitization refer to in terms of short-term memory?

A

increased responsiveness to mild stimuli, following strong or noxious stimulus
- enhances synaptic activity

PHGY 215 (3 decks)

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