Wk 8 Flashcards
The Nervous System
What are the functions of the nervous system?
- response to stimuli
- integration of body processes
- control/mediation of voluntary effectors (skeletal muscle)
- control/mediation of involuntary effectors (smooth muscle, cardiac muscle, glands, heart rate, BP)
- responsible for conscious thought, perception, emotions, personality, mind
What are the different functional classes of neuron?
- sensory (afferent); towards CNS
- motor (efferent); away from CNS
- interneurons; connect neurons in CNS pathway
What is the structure of a sensory neuron?
- cell body has no dendrites and presynaptic inputs
- located adjacent to spinal cord
- sensory receptor is end of axon
What is the structure of a motor neuron?
- cell bodies situated in CNS
- receive many inputs that influence outputs to other organs
What is the structure of an interneuron?
- entirely within CNS
- more complex the action the more interneurons required
How are the peripheral nerve fibres classified?
Group A
Group B
Group C
*Structure effects conductance velocity
What is Group A?
- large diameter
- highly myelinated
- transmit up to 150m/s (fastest)
What are the subgroups of Group A?
A alpha - somatic motor neurons, proprioceptor sensory neurons
A beta - sensory neurons for touch, pressure
A c - motor neurons to muscle spindles
A delta - some thermal and pain sensory neurons
What is Group B?
- intermediate diameter
- lightly myelinated
- transmit up to 15m/s
What is Group C?
- smallest diameter
- unmyelinated
- transmit up to 1m/s
What is a reflex arc?
An involuntary response to a stimulus (does not pass through brain - only neurons and spinal cord).
What are the components of a reflex arc?
- Sensory receptor - site of stimulus action
- Sensory neuron - transmit afferent impulses to CNS
- Integrating centre - within CNS
- Motor neuron - efferent impulses integration centre –> effector organ
- Effector - responds to efferent impulses
What are the 4 major regions of the brain?
- Cerebrum
- Diencephalon (thalamus, hypothalamus)
- Brain stem (midbrain, pons, medulla)
- Cerebellum
What is the primary function of the cerebrum?
- controls conscious thoughts and actions
- largest part of brain
- divided into temporal lobe, occipital lobe, parietal lobe, frontal lobe
What is the primary function of the diencephalon?
Thalamus
- relay station for sensory impulses
Hypothalamus
- homeostasis
- regulates autonomic function, body temp, fluid balance, hormone release
What is the primary function of the brainstem?
- includes the midbrain, pons, medulla oblongata
- control of cardiovascular system, respiratory rhythm
- vision/hearing
- consciousness, sleep/wake cycles
What is the primary function of the cerebellum?
- coordinates balance/posture
- automatic processing centre
- programs ongoing movements
What are the two divisions of the peripheral nervous system (PNS)?
- Sensory (afferent)
- Motor (efferent)
What are the two systems of the motor division?
- Somatic nervous system
- Autonomic nervous system
What are the functions of the somatic nervous system?
- supplies skeletal muscle
- CNS –> effector
- Release ACh to activate nicotinic receptors
What are the functions of the autonomic nervous system?
- supplies smooth, cardiac muscle and glands
- regulates internal environment
- operates without conscious control
What are the two divisions of the autonomic nervous system?
- Sympathetic
- Parasympathetic
*Antagonistic (opposite effects)
What is the sympathetic system?
- fight or flight
- associated with fear or stress
- releases NE
E.g. blood vessels, sweat glands, adrenal medulla
What is the parasympathetic system?
- rest and digest
- associated with housekeeping & conserving energy
- releases ACh
E.g. food digestion, pooing
