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PCAT: BIOLOGY > Nervous System > Flashcards

Nervous System Flashcards

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1
Q

what is the nervous system responsible for?

A
  • controlling body functions, enabling organisms to receive and respond to stimuli from external and internal environments
  • signals travel quickly 100m/s resulting in information transmission much faster than the endocrine system
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2
Q

what is the nervous system composed of

A
  • neurons (specialized nervous tissue) and neuroganglia (cells that support neurons)
  • work ti form the major oragans of the nervous system (brain, spinal cord and sensory organs)
  • divided into central NS and peripheral NS
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3
Q

what are the components of a neuron

A
  • neuons convert stimuli into electrochemical signals and conduct them through the nervous system
  • each neuron consists of denrites, a cell body and an axon
  • denrites = cytoplasmic extensions that recieve information and transmit it towards the cell body
  • cell body (soma) = contains the nucleus that controls the metabolic activity of the neuron

axon = long cellular process that transmits impulses or action potentials away from cell body

*axons end in synpatic terminals (also called boutons or knobs)

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4
Q

what covers the axon in most mammalian cells

A

insulated by myelin

  • prevents leakage of signal from axons and allows for faster impulses to be conducted
  • gaps between myelin = nodes of ranvier (where action potential actually propogates) via “hoping” conduction
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5
Q

what produces myelin

A
  • glial cells also called oligodendrocytes in the CNS and by schwann cells in the PNS
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6
Q

where are neurotransmitters released?

A

released in synaptic terminals into the synpase (synpatic cleft)

  • this is the gap between axon terminals of one cell and the dendrites on the next

*axons can be very long ex: travel from spinal cord to tip of foot

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7
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A
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8
Q

What are the 4 major cell types in the CNS and their roles

A

Astrocytes

  • maintain integrity of the BBB
  • regulate nutrient and dissolved gad conc
  • absorb and recycle neurotransmitters

Oligodendrocytes

  • Myelinate CNS axons and provide structural framework for CNS
  • *Microglia**
  • Remove cellular debris and pathogens

Ependymal cells

  • line brain ventricles
  • aid in the production, circulation and monitoring of cerebral spinal fluid
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9
Q

What are the major cell types of the PNS

A

Satellite cells

  • surround neuron cell bodies in the ganglia

Schwann cells

  • enclose axons in the PNS
  • aid in myelination of some peripheral axons
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10
Q

what is the function of neurons

A
  • specialized to recieve signals from sensory receptors and from other neruons
  • signals create action potentials whcih trevel length of axon to invade the nerve terminal causing neurotransmitter release @ synapse
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11
Q

what is the resting potential

A
  • potential difference at rest between the extracellular space and the intracellular space

*even at rest neuron is polarized

  • typical resting potential is -70mV (inside neuron more neg)
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12
Q

what causes the potential difference

A
  • caused by selective ionic permability of neuronal cell membrane
  • maintained by active transport by N+/K+ pump
  • 3 Na+ out and 2 K+ in
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13
Q

How does an action potential begin

A
  • if cell becomes sufficiently excited and depolarized (inside more pos) to reach the threshold potential then the voltage agted ion channels in nerve cell mem open

* action potential begins when voltage gated Na+ channels open in response to depolarization

  • Na+ rushes down electrochemical gradient INTO cell causing further rapid depolarization
  • Na+ influx causes next portion of axon to become depolarized and so on
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14
Q

what happens once the action potential reached the synaptic terminal

A
  • final voltage geted channel *this time calcium* opens alloing Ca2+ to rush in and trigger exocytosis of synpatic vesicles containing neurotransmitters
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15
Q

how does repolarization occur

A
  • occurs after signal has been propogated through a segment of the axon
  • the high voltage in that segment causes voltage gated K+ channels to open and K+ rushes down electrochemical gradient
  • voltage gated Na+ channels close and the Na+/K+ pump starts to pump Na+ out of the cell
  • returns cell to negative potential (repolarization)
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16
Q

what is hyperpolarization

A
  • during repolarization Na+/K+ pump works AND K+, meaning that K+ is still traveling out the cell so the insdie of the cell becomes MORE negative than resting potential
  • this called hyperpolarization and results in a refractory period
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17
Q

what is teh refractery period

A
  • period of time after an action potential during which new ones are very difficult - impossible to initiate
  • allows neuron time to regenerate neurotransmitter and ensures for action potential to move only in one direction towards the terminal
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18
Q

action potential is called an _____ response

A
  • all or none
  • if and only if the threshold membrane potential is reached can an action potential with a consistent size and duration eb rpoduced
  • neurons fire maximally or not at all
  • stimulus is coded by the frequency of action potentials NOT their magnitude
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19
Q

what is impulse propogation

A
  • although axons can only propogate action potentials bidirectionally information transfer will occur only in one direction: dendrite to synpatic terminal
  • thi is bc synpases operate only in one direction bc refractory priods make backward travel not possible
  • axons do propgate action potential at different speeds: the greater the diameter of axon the more ehavily its myelinated the faster impulses travel
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20
Q

what is the synapse

A
  • gas between axon terminal of one neuron (presynaptic neuron) and the dendrites of antoher (post synpatic neuron)
21
Q

what are effector cells

A

neurons can communicate with post synpatic cells other than neurons such as cells in muscles or glands: called effector cells

22
Q

how does neurotransmitter release work

A
  • when aciton potential arrives @ enrve terminal and depolarizes it the synpatic cesicles fuse w/ postsynpatic membrane and release neurotransmitter into synpase
  • neurotransmitter diffuses across synpase and interacts w/ receptors on post synaptic membrane
  • leads to depolarization of post synpatic cell and firing of action potential
23
Q

how is neurotransmitter removed

A
  • can be taken back up into nerve terminal via uptaker protein where it can be reused or degraded
  • can be deraded by enzymes ocated in synpase (acetylcholinesterase inactivates the neurotransmitter acetylcholine)
  • can diffuse out synpase
24
Q

what is the effect of curare

A
  • blocks postsynaptic nicotinic acetylcholine receptors such as those on muscles
  • acetylcholine cannot interact leading to muscle relaxation and paralysis by blocking ability to contract muscles
25
Q

what is the effect of botulinum toxin

A
  • prevents release of acetylcholine from presynaptic membrane and results in paralysis
26
Q

what is the effect of acetylcholinesterases

A
  • used as nerve gases in the insecticide parathion
  • substances inhibit activity of acetylcholinesterase enzyme responsible for degrading acetylcholine released int he synpase
  • as a result it acetylcholine is degraded and continues to affect the post synpatic membrane

*no coordinating muscular contraction can take place

27
Q

what are afferent neurons

A
  • carry sensory information about external and internal environment to braina dn spinal cord
28
Q

what are efferent neurons

A
  • carry motor commands from brain and spinal cord to various parts of the body (muscles, glands)
29
Q

what are interneurons

A
  • participate only in local circuits linking sensory and motor neurons in brain and spinal cord
  • their cell bodies and nerve terminals are in the same location
30
Q

what is a network of nerve fibers called

A
  • plexus

*nerves are essentailly bundles of axons covered with connective tissue

31
Q

Neuronal cell bodies often cluster together, clusters are called ___ in the PNS and ____ in the CNS

A

ganglia in PNS and nuclei in CNS

32
Q

what are the branches of the CNS

A

brain and spinal cord

33
Q

what are the branches of the PNS

A

somatic and autonomic

  • auonomic is broken into sympathetic and parasympathetic
34
Q

what is the brain/ what does it consist of

A
  • mass of neurons inside the skull
  • functions include interpreting sensory information, forming motor plans and cognitive function (thinking)
  • consists of: puter portion of cell bodies called grey matter and innter portion of myelinated axons called white matter
  • also divided into forebrain, midbrain and hindbrain
35
Q

what is another name of the forebrain

A

prosencephalon

36
Q

what does the forebrain consist of what are the roles

A
  • telencephalon and diencephalon

Telencephalon

  • contains cerebral cortex: highly convoluted gray matter seen on surface of the brain
  • processes and integrates sensory input and motor responses: important for creative thought
  • olfactory bulb = center for reception and integration of smell related input

Diencephalon

  • contains thalamus and hypothalamus
  • thalamus = relay and integration center for spinal cord and cerebral cortex
  • Hypothalamus = controls visceral functions such as hunger, thirst, sex drive, water balance, blood pressure and temp regulation
    • important role in endocrine system
37
Q

what is te role of the midbrain and waht is the other name

A
  • also called mesencephalon
  • relay center for visual and auditory impulses
  • important role in motor control
38
Q

what is the role of the hindbrain

A
  • also called Rhombencephalon
  • the hindbrain is the posterior part of the brain
  • consists of cerebellum, the pons, and medulla

Cerebellum

  • helps to modulate motor impulses initiated by the cerebral cortex and is important in maintenance of balance, hand-eye coordination and timing of rapid movements

Pons

  • act as a relay centre to allow the ortex to communicate with the cerebellum

Medulla (medulla oblongata)

  • controls many vital functions: breathing, heart rate, gastrointestinal activity

**togethere all 3 of these make the brainstem

39
Q
A
40
Q

what is the spinal cord/ its role

A
  • elongated extension of the brain acting as a conduit for sensory information to the brain and motor information from the brain
  • can also integrate simple motor responses (reflexes) by itself
41
Q

what are the components of the spinal cord

A
  • cross section shows outer white matter containing sensory and motor axons and inner gray matter w/ nerve cell bodies
  • sensory information enters via dorsal horn: these cell bodies of sensory neurons are located in the dorsal root ganglia
  • all motor information exists the spinal cord via ventral horn
42
Q

how are different reflexes process by the spinal cord

A
  • in simple reflexes lke knee-jerk sensory fibers (entering through the dorsal root ganglion) synpase directly on ventral horn motor fibers
  • other reflexes include interneurons between the senesory and motor fibers alloing for some processing in the spinal cord
43
Q

Role of peripheral nervous system

A
  • consists of nerve and ganglia
  • sensroy nerves enter the CNS and the motor nerves that leave the CNS are part of the PNS
  • constains somatic and autonomic each having both motor and sensory components
44
Q
A
45
Q

what is the SNS

A
  • somatic nervous system
  • innervates skeletal muscle and is responsible for voluntary movement and reflex arcs (pathways that control motor reflexes
46
Q

what is the ANS

A
  • autonomic nervous system
  • called the involuntary nervous system: operates w/o concious control
  • innervates cardian and smooth muscle: smooth msucle is located in areas like blood vessels, digestive tract, bladder and bronchi
  • important for blood pressure regualtion, gastrointestinal motility, excretion, respiration, an reproduction
  • contains sympathetic and parasympathetic which generally act in opposition to eachother
47
Q

explain the sympathetic nervous system

A
  • acts to conserve energy and restore body to resting activity levels: rest and digest
  • acts to lower heart rate and inc gut motility
  • it innervates the thoracic and abdominal viscera called vagus nerve
  • acetylcholine is the primary neurotransmitter
48
Q

describe the parasympathetic nervous system

A
  • responsible for fight or flight responses that ready the body for action in an emergency situation
  • increases vlood rpessure and heart rate, inc blood flwo to skeletal muscles, dec gut motility, dilates bronchioles to inc gas exchange
  • norepinephrine is the primary neurotransmitter
49
Q
A

PCAT: BIOLOGY (18 decks)

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