Nervous System - CTL Flashcards
wk 8
What are the three functions of the nervous system?
Sensory, integrative and motor
Describe the motor functions of the nervous system
Control of voluntary effectors (skeletal muscles) and mediation of voluntary reflexes.
Conscious thought, perception, emotions, personality and the mind
What are the three functional classes of neurons?
sensory, motor and interneurons
What are the properties of sensory neurons?
Afferent = transmit impulses TOWARDS the CNS
devoid of dendrites and presynaptic inputs
located in adj to spinal cord
peripheral ending of axon = sensory receptor
What are the properties of motor neurons?
carry impulses away from the CNS
Receive many inputs to influence neuron output to effector organ
Structure
Cell bodies in CNS
What are the properties of interneurons?
connect between neurons in CNS pathway
Structure
99% of neurons
Entirely in CNS
Where are the sensory receptors of a neuron?
in sensory neurons: peripheral ending of axon is modified as a sensory receptor
The more complex the action =
More interneurons interposed between afferent and efferent neurons
How are fibres classified?
according to the direction they transmit impulses?
Nerves can be a mixture of fibres. True or False?
True - Most nerves are a mic: afferent and efferent fibers and somatic and autonomic fibers. Pure nerves are rare
What are the properties of Group A fibres?
Large diameter
Myelinated somatic sensory and motor fibers of the skin, skeletal muscles and joints
Transmit up to 150m/s
What are the properties of Group B fibres?
Intermediate diameter
Lightly myelinated
Transmit 15m/s
What are the four types of Group A fibres?
A-a
A-b
A-y
A-8
What is the function of A-a fibres?
somatic motoneurons
Proprioception
What is the function of A-b fibres?
touch and pressure
What is the function of A-y fibers?
motor to muscle
spindles
What is the function of A-delta fibers?
pain, cold and touch
What is the function of Group B fibres?
Preganglionic autonomic
What is a postganglion neuron?
begins in ganglion and travels to the smooth muscle or gland that is been innervated
What is a preganglionic neuron?
originated in CNS and travels from here to a ganglion.
What are the 5 general components of a neural reflex arc?
Sensory receptor : site of stimulus action
Sensory neuron : transmits afferent impulses to CNS
Integrating Centre : either monosynaptic or polysynaptic region within CNS
Motor Neuron: conducts efferent impulses from integration center to effector organ
Effector: muscle fibre/ gland cell responds by contracting or secreting
Where is the integrating sensor in the patellar reflex?
Spinal cord
Where is the sensory receptor in the patellar reflex?
muscle spindle
What are the two main parts of the nervous system?
CNS and PNS
What is the PNS composed of? What is it’s purpose?
Cranial nerves and spinal nerves
communication lines between the CNS and rest of the body
What are the two divisions of the PNS?
Sensory (afferent) and Motor (efferent) divisions
what are the two fibres of the sensory division?
somatic and visceral
What are the two systems of the motor division?
Somatic nervous system (SNS) and Autonomic nervous system (ANS)
Describe the Somatic nervous system.
Voluntary = somatic motor
conducts impulses from CNS to skeletal muscles
axons exrend from CNS to effector
Describe the ANS.
Involuntary = visceral motor
impulses from CNS to cardiac muscles, smooth muscles and glands
regulates internal environment
without conscious control
What are the 4 main regions of the brain
cerebrum, Diencephalon, Brain Stem and Cerebellum
What is the surface layer of the cerebrum called?
cerebral cortex
What are the primary functions of the cerebrum?
Processes sensory and motor information
Site of conscious thought, sensation, intellect, memory and complex movements
Where is the Diencephalon?
On top of the brainstem, enclosed by the cerebral hemispheres
What is the primary function of the thalamus?
Relay station for sensory impulses passing into the cortex
What are the two main parts of the Diencephalon region?
Thalamus and hypothalamus
What are the primary functions of the hypothalamus?
Regulates autonomic function, body temp, fluid and hormone release to maintain homeostasis
what are the three components of the brainstem?
pons, medulla oblongata and midbrain
What are the major functions of the brain stem?
Reflex center: vision and hearing
Consciousness, sleep/wake cycle
Autonomic control of cardiovascular system
Respiratory rhythm
Convey ascending and descending information
What is the effector of the somatic nervous system
skeletal muscle
what is the functional role and structure of somatic nervous system?
stimulatory
heavy myelinated axon
What are the two componets of the autonomic nervous system?
Sympathetic and parasympathetic nervous system
What is the function of the ANS?
Stimulatory/ inhibitory- depends on neurotransmitters and receptors of effector
what is the NT effector of the somatic nervous system?
ACh
What is the NT effectors of the parasympathetic ANS?
ACh
What do all Somatic nervous system Neurons release?
ACh to activate nicotinic receptors on skeletal muscle
What is the neurotransmitter of sympathetic?
Norepinephrine
what are the actions of interneurons?
neural circuit= flow of signals between sensory and motor neurons
what type of fibres are somatic and autonomic?
visceral
how are nerve fibres classified?
according to their diameter. A, B or C
How fast can Group A fibres transmit and why?
150m/s due to large diameter and myelinated neurons
What is the diameter of:
A-a
A-b
A-y
A-gamma
a= 12-20
b= 5-12
y=3-6
gamma= 2.5
what is the diameter of Group B fibers?
less than 3
what is the diameter of Group C fibres for pain and temperature?
0/4-1.2
what is the diameter of Group C fibres for postganglionic autonomic?
0.3-1.3
What is the Autonomic nervous system?
Division of motor neurons that:
supplies smooth, cardiac muscle and glands
regulates internal environment
and is divided into sympathetic and parasympathetic
What is the fight or flight response?
sympathetic
what is the rest and digest respomse?
parasympathetic
Do symapthetic and parasympathetic divisions act antagonistically or agonistically?
antagonistically = opposite effects
what are the two responses in the patellar reflex?
Positive response: quadricep contracts
reduction of MP: hamstring relaxes because when there is a reduction of MP it becomes less likely to fire a AP
What is the overall function of the sympathetic division?
mobilizes body systems during activity
what is the overall function of the parasympathetic division?
conserves energy and pormotes house-keeping functions at rest
What do all somatic motor neurons release and what does it do?
all release acetylcholine to activate nicotinic receptors on skeletal muscle.