Intro to physiology Flashcards
Main function of CNS
Sensory integration
Motor commands
Areas of brain involved with CNS
Cerebral cortex
Brainstem
Cerebellum
Regions of the spinal cord
Cervical
Thoracic
Lumbar
Sacral
Inputs in the CNS from PNS
Sensory division
Inputs in the PNS from CNS
Motor division
Divisions of motor division
Somatic nervous system
Autonomic nervous system
Somatic nervous system
Skeletal muscles
Divisions of autonomic nervous system
Parasympathetic
Sympathetic division
Enteric division
Enteric division
Digestion
How many segments does the spinal cord have
31 - each with a motor and sensory nerve root
How does sensory info enter the spine
Via the dorsal root
How does motor info leave the spine
Via the ventral root
Ascending tracts in the spine
Carry sensory info to CNS
Descending tracts in the spine
Carry CNS info to motor neurone which control movement/ posture
Lateral corticospinal tract is most important function
Direction of impulse in sensory neurons
From receptors, down dendrite to axon terminal
Direction of impulse in motor neurone
From dendrites, down axon to axon terminal
Types of axonal projection in neurones
Goes to distant brain area
Stays in local brain area
Diff dendritic patterns on neurons
Pyramid-shaped spread of dendrites
Radial-shaped spread of dendrites
Types of motor neurons
Upper motor neurons
Lower motor neurons
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
Lower motor neurons
Found in the brain stem and spinal cord
Directly responsible for communicating with the effector organs
Types of lower motor neurons
Alpha
Beta
Gamma
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
