Nervous System Organization Flashcards
(78 cards)
1
Q
Nervous System is Composed of:
A
Central Nervous System and Peripheral Nervous System
2
Q
Central Nervous System
A
Brain or spinal cord
3
Q
Peripheral Nervous System
A
Outside the brain or spinal cord. Nerve fibers that carry information
4
Q
PNS subdivided into two divisions
A
Afferent and Efferent
5
Q
Afferent
A
- Carries information from sensors to the CNS
- Transmits information of the external environment and of internal activities (visceral stimuli) regulated by the nervous system
6
Q
Efferent
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- Transmits information from the CNS to effector organs (muscles, glands, and other organs)
7
Q
Subdivisions of Efferent
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Somatic and autonomic
8
Q
Somatic
A
- Voluntary system
- Consists of fibers of the motor neurons that supply the skeletal muscles
9
Q
Autonomic
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- Involuntary system
- Fibers that innervate smooth muscle, cardiac muscle, glands, and other on-motor organs
- Sympathetic and parasympathetic
10
Q
The nervous system evolved from …
A
Basic Reflex Arcs
11
Q
Multiple synaptic connections allow for …
A
inputs from “higher” integrators to modify basic reflex arcs
12
Q
Afferent Neurons
A
- Make up the afferent divisions of PNS
- The peripheral ending has a sensory receptor that generates an AP in response to stimulus
- The cell body is located OUTSIDE to the spinal cord in a GANGLION in the dorsal root
- Usually no dendrites, long peripheral axon (afferent fiber), short central axon passes from the cell body to the spinal cord with multiple terminals
13
Q
Efferent Neurons
A
- Cell bodies originate WITHIN the CNS and axons (efferent fibers) leave the CNS to the muscles or glands they innervate
14
Q
Interneurons
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- Lie ENTIRELY WITHIN THE CNS and makeup about 99% of neurons in the body
- Exist between efferent and afferent neurons to integrate peripheral responses to peripheral information
15
Q
Five fundamental components of REFLEX ARCS
A
- All reflex arcs with a SENSORY RECEPTOR - transduces an environmental cue that is converted to an AP (example: retina, muscle, spindle, skin)
- Arc contains a SENSORY NEURON (afferent) that carries the AP from the receptor to the CNS. Enters the spinal cord through the dorsal roots.
- Arc SYNAPSES in the CNS (usually more than 1 synapse)
- A MOTOR NEURON (efferent neuron) carries the AP to the target organ (effector). Motor nerves leave the spinal cord through the ventral root
- TARGET ORGAN (effector organ) that causes the reflex response
16
Q
The PNS also harbor _______ that contain somas of most sensory neurons
A
ganglia
17
Q
Ganglia
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Swellings containing aggregations of neuron cell bodies and processes
18
Q
Reflexes are _______ (right to left) without higher order intervention (from the brain)
A
coordinated
19
Q
Efferent Components of the Nervous System
A
- Somatic
- Autonomic
- Enteric
20
Q
Somatic
A
- Control of skeletal muscle (body motion, speech, breathing, etc)
- VOLUNTARY system
- Motor neurons extend from the CNS directly to target tissue
21
Q
Somatic Motor Neurons
A
Do not have a peripheral neuron-to-neuron synapse
22
Q
Autonomic
A
- Regulates involuntary functions (automatic)
- Prior to terminating at target tissues, synapses occur at ganglia in the PNS
- Neurons divided into pre and post ganglionic creates = TWO NEURON CHAIN
- Parasympathetic and Sympathetic
23
Q
Sympathetic
A
- Fight or flight response
- Ganglia primarily near the spinal cord
- SHORT preganglionic neurons emanating from the spinal column
- Release norepinephrine or noradrenaline (NE) termed adrenergic neurons
24
Q
Parasympathetic
A
- Rest and digest response
- Ganglia at or near the effector organ
- LONG preganglionic neurons from the brain or sacral region
- Release of acetylcholine (termed cholinergic neurons)
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Pre-ganglionic neurons...
of the autonomic system all release acetylcholine (ACh)
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Post-ganglionic neurons...
of the autonomic system all release different neurotransmitters
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Adrenal Medulla
- Modified ganglion that reinforces the sympathetic system
- Directly releases hormones into the blood
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Epinephrine
Adrenaline
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Each autonomic neurotransmitter and medullary hormone creates..
Either activating or inhibiting responses in different tissues
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Tissue responsiveness is then controlled by..
Receptors
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Responses to the same neurotransmitters (norepinephrine or epinephrine) can..
produce either excitatory/activating or inhibitory responses
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Enteric:
- Regulates involuntary functions (automatic) of the digestive tract
- Can act independently of the rest of the nervous system
- Digestive activities are influenced by the autonomic system
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Sympathetic examples:
- Acetylcholine
- Norepinephrine/noradrenaline
- Skeletal muscle contraction
- Bronchiole Tubes (lungs) dialate
- Adrenergic Receptors
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Parasympathetic examples:
- Rest + Digest
- Acetylcholine
- Increased Urinary Output
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Cephalization
Organization of the brain into clusters of neurons that perform similar function
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Olfactory Cortex
Smell
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Occipital cortex
Visual
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Auditory Cortex
Hearing
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Association Cortex
- Location of complex processing
- Both sensory and motor
- Memory
- Future, planning
- Communication (Language)
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(Cerebral Cortex Cerebrum) Primary Motor Cortex
- Function: Controlled Motor Output
- Cortical linkage to specific regions of the body
- Reflex movements occur without input from PMC
- Sensations of temperature and pain
- Kinesthetic senses (muscle/joint input)
- Vestibular Senses (Balance)
- Exerts voluntary control over movement produced by skeletal muscles
- Opposite side of the is regulated
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Proprioception
Sense of body position based on input from skin
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Cerebellum
- Function: Function: Maintain proper position of the body in space and coordination of motor activity
- Integrative, sunbconscious CONTROL OF MOTOR ACTIVITY
- MODIFY OUTPUT FROM MOTOR CENTERS
- Maintain balance, helps coordinate fast, phasic motor activity, and enhances muscle tone
43
Higher mammals have three parts of the cerebellum
- Vestibulocerebellum
- Cerebrocerebellum
- Spinocerebellum
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Vestibulocerebellum
Balance and control of eye movement
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Cerebrocerebellum
Planning and initiating voluntary activity by providing input to the cortical motor areas
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Spinocerebellum
Enhances muscle tone and coordinates skilled voluntary movements
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Brain Stem
- Function: Coordinating, LIFE-SUSTAINING FUNCTIONS (aka breathing and circulation)
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Hypothalamus
- Function: INTEGRATING CENTER for many HOMEOSTATIC FUNCTION
- Part of limbic system
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Protective structures
1. Cranium (skull) and vertebral column
2. Meninges
3. Cerebral Spinal Fluid
4. Blood-brain barrier
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Cranium (skull) and vertebral column
- Separation of afferent and efferent (dorsal root/horn and ventral root/horn)
- White matter = myelination/high axons
- Gray Matter = Cell bodies (somata/dendrites)
- Cerebrospinal fluid/canal
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Cranium (skull) and vertebral column Primary Regions
- Cervical
- Thoracic
- Limbar
- Sacral
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Meninges
- Protective and nourishing membranes, lie between the bone and nervous tissue
- a) Dura matter
- b) Arachnoid
- c) Pia Mater
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Dura Mater
Tough, inelastic covering beneath the bone
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Arachoid
Delicate, highly vascularized layer that looks like a cobweb
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Pia Mater
Innermost layer that adheres to the surface of the brain and spinal cord
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Cerebral Spinal Fluid
- Specialized fluid for shock absorption (brain floats) a nd specialized extracellular environment
- Higher Na+ and lower K+ than blood
- Produced by selective transport across membranes of CHOROID PLEXUS (ChP)
- Produced in middle of brain
- Flows thru ventricles within interior of brain and thru spinal canal
- ChP>Lateral Vents>Third Vent>Fourth vent>Spinal Canal
- CFS flows out of the third and fourth ventricle into the subarachnoid space and between meningeal layers over the entire surface of brain/spinal cord
- Supports brain and cushions
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Ependymal Cells
Ciliated cells that promote the movement of CSF
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Transporters that regulate CSF
Na, K, Cl, Glucose
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CSF is reabsorbed into blood thru
arachnoid villi
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Blood-brain barrier
- Highly selective subcellular barrier
- Regulates exchange between blood and brain within vasculature that penetrates within brain
- Limits access to blood-borne materials
- Astrocytes contribute to barrier but tight junctions do most of work
- Lipid soluble compounds (oxygen carbon dioxide, steroid hormones, alc) can idssolve thru capillary membranes
- Water molecules can pass thru
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Brain capillaries are specialized with ___________ that completely seal capillary wall so nothing can pass between cells
tight junctions
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Amino Acids, glucose, ions
transported by selective membrane carriers and primary active transport gets glucose across
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Why does the hypothalamus not have a blood-brain barrier?
Because it must sample the blood to sense changes in levels & release compounds direct;y into the blood to their site of action
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Short-term:
- Immediate storage
- Limited capacity
- Lasts seconds to hours
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Long-term:
- Delayed storage
- Large capacity
- Retained for days/years
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Consolidation
- Info from short-term stores must be processed into long-term
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Both short and long-term memory are utilized in practical context within the ______.
Working memory
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Short term: What is SYNAPTIC PLASTICITY?
- Changes in synaptic strength over time
- Can occur at level of:
> Presynaptic cell: facilitation and anti-facilitation
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Short term: Presynaptic cell
Changes in the amoutn of neurotransmitter released across synaptic cleft
70
Changes in synaptic plasticity contribute to either ______ or _______
habituation, sensitization
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Habituation
- Decreased responsiveness to repetitive presentations of an indifferent stimulus (neither rewarding/punishing)
- aka building habits
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Sensitization
- Increased responsiveness to mild stimuli following strong or noxious stimulus
- Heightened responses (survival)
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Many habituation and sensitization responses are remodeled via ______ and _______ within presynaptic neurons
facilitation, anti-facilitation
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Long-term: What is SYNAPTIC PLASTICITY?
- Changes in synaptic strength over time
- Can occur at level of:
> Postsynaptic cell: long-term potentiation(high) and long-term depression(low)
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Long-term potentiation(high)
- Involves DYNAMIC formation or loss of synaptic connections
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Biological Clocks
- Mammal shave internal & integrated biological clocks that rhythmically modulate the function in cells, tissues, and organs
- Allows for the temporal (timed) organization of different functions
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Examples of biological clocks
- Being either awake and asleep creates oscillations in different functions, such as body temp and urinary function
- Occurs in isolated subjects w/o any sense of time
- Regulated by environment but they are INTRINSIC MECHANISMS
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Examples of intrinsic mechanisms
- Dawn triggers many animals to change activity and oxygen consumption
