Intro to physiology Flashcards by Jasmine Sappor

Main function of CNS

Sensory integration

Motor commands

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Areas of brain involved with CNS

Cerebral cortex
Brainstem
Cerebellum

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Regions of the spinal cord

Cervical
Thoracic
Lumbar
Sacral

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Inputs in the CNS from PNS

Sensory division

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Inputs in the PNS from CNS

Motor division

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Divisions of motor division

Somatic nervous system

Autonomic nervous system

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Somatic nervous system

Skeletal muscles

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Divisions of autonomic nervous system

Parasympathetic
Sympathetic division
Enteric division

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Enteric division

Digestion

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How many segments does the spinal cord have

31 - each with a motor and sensory nerve root

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How does sensory info enter the spine

Via the dorsal root

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How does motor info leave the spine

Via the ventral root

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Ascending tracts in the spine

Carry sensory info to CNS

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Descending tracts in the spine

Carry CNS info to motor neurone which control movement/ posture
Lateral corticospinal tract is most important function

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Direction of impulse in sensory neurons

From receptors, down dendrite to axon terminal

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Direction of impulse in motor neurone

From dendrites, down axon to axon terminal

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Types of axonal projection in neurones

Goes to distant brain area

Stays in local brain area

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Diff dendritic patterns on neurons

Pyramid-shaped spread of dendrites

Radial-shaped spread of dendrites

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Types of motor neurons

Upper motor neurons

Lower motor neurons

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Upper motor neurons

Originate in the motor cortex of the brain/ brain stem and transmit signals to relay or lower motor neurons
Mainly initiates voluntary movement

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Lower motor neurons

Found in the brain stem and spinal cord

Directly responsible for communicating with the effector organs

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Types of lower motor neurons

Alpha
Beta
Gamma

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Alpha motor neurons

Responsible for controlling muscle contractions involved in voluntary movement through contracting extrafusal muscle fibres

Extrafusal fibres

Standard muscle fibres

Beta motor neurons

Least common | Stimulate intrafusal muscle fibres

Intrafusual fibres

Muscle fibres found deep into the muscle

Gamma motor neurons

Control muscle contraction in response to external forces through the intrafusal fibres Regulate the muscle response to stretch

Neuroglia cells

Neural support and protection

Neuroglia cells in CNS

Oligodendrocytes Astrocytes Microglial Ependymal cells

Oligodendrocytes

Myelin of CNS

Astrocytes

Long processes from blood-brain barrier between blood and cerebrospinal fluid

Microglial

Phagocytosis; converge on sites of injury or infection

Ependymal cells

Facilitate movement of cerebrospinal fluid

Neuroglia cells in PNS

Schwann cells Satellite cells Enteric glial cells

Where are satellite cells found

Sensory and autonomic ganglia

Where are enteric glial cells found

Gut wall

Gilia

Specialised cells that support and nourish neurons that arent neurons

RMP

Resting Membrane Potential The inside of a cell is always -ve relative to the outside Most cells have a resting membrane potential of between -40 and -100 mV

Why does the RMP develop

Semi permeable nature of the cell membrane Unequal distribution of ions inside and outside of the cell Presence of ion pumps (active transport)

Ionic basis of RMP

Na/K pump - 3 Na out and 2 K in [K+] is higher inside so diffuses out VG Na+ channels closed Cytoplasm has large organic anions

Action potential

Transient depolarisation triggered by a depolarisation beyond a threshold Results in opening and closing of Na+ and K+ channels in axon membrane

Propagation of action potential in unymelinated neurons

Depolarisation will spread out from the active site | Magnitude of current decreases w/ increasing distance w/ active site

Propagation of action potential in myelinated neurons

Depolarisation occurs at Nodes of Ranvier only (Saltatory Conduction)

Axoplasmic transport processes

Anterograde | Retrograde

Anterograde

Organelles and vesicles move along microtubules via microtubule-dependent motor proteins, kinesins

Kinesins

ATP-ases

Retrograde

Material moved back to cell body by Dynein motor proteins

Dynein

ATP-ase

Function of autonomic nervous system

Maintenance of homeostasis

Simple involuntary reflexes

Baroreceptor reflex Micturition Salivation Pupillary light reflex

Factors determining velocity of an action potential

Temperature Axon diameter Presence or absence of myelin sheath

How does temp determine velocity of action potential

The higher the temp, the faster the conduction velocity

How does axon diameter determine velocity of action potential

Larger the axon diameter, the faster the conduction velocity

Axon hillock

Where action potential is summed

Types of summation

Spatial | Temporal

Spatial summation

Sev presynaptic neurones connect to post synaptic neurones | Each releases a transmitter so the conc increases in the synapse

Temporal summation

Single presynaptic neurone relates neurotransmitter due to several ap's in a short time