Nervous system Physiology (1) Flashcards
What is this an image of?
Nervous tissue
Label this neuron
List the parts that make up a neuron?
Cell body
Nucleus
Dendrites
Myelin Sheath
Node of Ranvier
Axon
Schwann’s Cells
Axon terminals
What is the cell body of a neuron?
Cell body, also known as the perikaryon (per -i-KAR-e ̄-on) or soma, contains a nucleus surrounded by cytoplasm that includes typical cellular organelles such as lysosomes, mitochondria, and a Golgi complex. Neuronal cell bodies also contain free ribosomes and prominent clusters of rough endoplasmic reticulum, termed Nissl bodies.
What is a dendrite?
The receiving or input portions of a neuron. The plasma membranes of dendrites (and cell bodies) contain numerous receptor sites for binding chemical messengers from other cells. Dendrites usually are short, tapering, and highly branched. In many neurons the dendrites form a tree-shaped array of processes extending from the cell body. Their cytoplasm contains Nissl bodies, mitochondria, and other organelles.
What is an axon?
A neuron propagates nerve impulses toward another neuron, a muscle fiber, or a gland cell.
An axon is a long, thin, cylindrical projection that often joins to the cell body at a cone-shaped elevation called the axon hillock. The part of the axon closest to the axon hillock is the initial segment. In most neurons, nerve impulses arise at the junction of the axon hillock and the initial segment, an area called the trigger zone, from which they travel along the axon to their destination. An axon contains mitochondria, microtubules, and neurofibrils.
Because rough endoplasmic reticulum is not present, protein synthesis does not occur in the axon. The cytoplasm of an axon, called axoplasm, is surrounded by a plasma membrane known as the axolemma (lemma sheath or husk).
What are neurons?
Neurons are electrically excitable cells, their function is to process and transmit information. Neurons communicate using electrical and chemical synapses (synaptic transmission)
The process that underlies electrical synaptic transmission is the action potential.
An action potential is an electrical signal that can be propagated through a nerve
An action potential is generated because the neuron membrane is electrically excitable.
Although neurons can occur in different shapes and sizes, they contain common structural elements
Describe the stucture of a neuron?
Soma (cell body)
- contains nucleus and other important material that provides for the life processes in the cell
Dendrites
- receive the messages between neurons
Axon
- links together the cell body and the terminal buttons
Terminal buttons (axon terminals)
- where the message is passed over to another neuron, across the synapse
What are each of these basic neurons?
How is an action potential created?
What is the cells resting potential?
It is the difference between the intra and extra cellular environments, that is exploited to produce an action potential.
The membrane has selective ion channels through which some ions, such as sodium (Na+), chloride (Cl-), potassium (K+) and calcium (Ca2+), can diffuse.
Neuronal membranes also use selective pumps to move ions against the concentration gradient
Because ions have electrical charge, the concentration gradient creates an electrical potential (about -70 millivolts) between the inside and the outside of the cell this is the cells resting potential
Explain what is happening in this diagram?
What are synapses?
These occur at the boundary of each nerve cell where it meets another nerve, muscle or endocrine cell.
The nerve impulse can be transmitted not only by an electrical signal but also by a chemical signal.
The substances which act as chemical signallers are called neurotransmitters.
Label this image
Where would electrical synapses typically be found?
- Anywhere, where a fast synchronous response is required for example:
- Retina
- Reflexes
- More interestingly they are found throughout the brain cortex and act in tandem with chemically driven neurotransmission.
- It is thought this gives the brain additional ‘plasticity’ because the mode of transmission is temporally different (chemical synapses are slower)*
Label this image
Name some common neurotransmitters
Acetylcholine
Norepinephrine
Dopamine
Serotonin
Glutamate
GABA- Gamma-Aminobutyric Acid
Enkephalins- Enk
What are the effects of the sympathetic and parasympathetic systems?
Most of your organs are supplied with both sympathetic and parasympathetic nerves
The two systems have opposing effects:
The sympathetic system is the “fight or flight” system
The parasympathetic system is in control in the normal relaxed state “rest and digest” system
Which system constricts the pupil?
Parasympathetic
Sympathetic dilates
Which system stimulates salivation?
Parasympathetic
Sympathetic inhibits salivation
Which system accelerates heart?
Sympathetic
Parasympathetic inhibits heart
Which system relaxes bladder?
Sympathetic
Parasympathetic contracts bladder
Which system stimulates digestive activity?
Parasympathetic
Sympathetic inhibits digestive activity
Which system relaxes rectum?
Parasympathetic
Sympathetic contracts rectum
Which system stimulates glucose production by the liver?
Sympathetic
Parasympathetic stimulates gall bladder
Which system constricts the bronchi?
Parasympathetic
Sympathetic relaxes bronchi
Which system stimulates the secretion of epinephrine and norepinephrine from the kidney?
Sympathetic
How many cervical nerve pairs are there?
8
How many thoracic nerve pairs are there?
12
How many lumbar nerve pairs are there?
5
How many sacral nerve pairs are there?
5
How many coccygeal nerve pairs are there?
1
What is supplied by the cervical nerves?
C1,2,3- control the head and neck
C4- helps control the shoulders as well as the diaphragm
C5- controls upper body muscles like the deltoids and the biceps
C6- controls the wrist extensors and also provides some innervation to the biceps.
C7- controls the triceps
C8- controls the hands
What is supplied by the thoracic nerves?
- Chest muscles
- Abdominal muscles
What is supplied by the lumbar nerves?
Leg muscles
What is supplied by the sacral nerves?
- Bowel, bladder
- Sexual function
Label this image
Label and fill in the blanks
Explain the spinal cords physiology?
What does the information received here control?
What are the two pathways?
The spinal cord sends and receives information from the entire body, this information controls sensation, movement and autonomic function.
There are two pathways consisting of axon bundles
- The descending pathway
- The ascending pathway
Explain the descending pathway?
The descending pathway-voluntary movement control, information comes from the cortico-spinal tract in the brain to motor neurons in the spinal cord and on to the final destination.
Explain the ascending pathway?
The ascending pathway- carries information from sensory neurons in the spinal tract to the brain, this gives information about body position, temperature, pain etc
Label the reflex arc
Explain the reflex arc?
- The stimulus is detected by a receptor this can be the end of a dendrite or specialist receptor cell
- The sensory neuron passes this information onto the CNS
- The CNS (brain or spinal cord) interprets and integrates this message
- A motor neuron carries the message to the effectors
- The effectors, a muscle or gland then undertakes a response. Reflex arcs generally involve large numbers of connecting neurones in the CNS
Label where the neurons go
Label the types of neuron
What can cause a SCI?
How is the level of neurological injury determined?
Where are the tetraplegia and paraplegia regions?
- This can result from trauma or disease
- The level of neurological injury is
determined by the lowest point on the
spinal column below which there is
decrease or absence of feeling.
•Injuries to C1-T2 can result in tetraplegia (quadriplegia)
Injuries between T2 and S5 can result in
paraplegia
Complete this diagram
Explain the role of C1-C3 nerves?
C1, C2, and C3 (the first three cervical nerves) control the head and neck, including movements forward, backward, and to the sides.
These nerves also play key roles in breathing.
The C2 dermatome handles sensation for the upper part of the head, and the C3 dermatome covers the side of the face and behind the head.
(C1 does not have a dermatome.)
Explain the role of the C4 nerve?
C4 helps control the shoulders as well as the diaphragm—for breathing. The C4 dermatome covers the neck and top of the shoulders.
Explain the role of the C5 nerve?
C5 controls upper body muscles like the deltoids and the biceps. The C5 dermatome covers the shoulders and outer part of the arm down to about the elbow or close to the wrist.
Explain the role of the C6 nerve?
C6 controls the wrist extensors (muscles like the extensor carpi radialis longus, extensor carpi radialis brevis, and extensor carpi ulnaris that control wrist extension and hyperextension) and also provides some innervation to the biceps. The C6 dermatome covers the top of the shoulders and runs down the side of the arm and into the thumb side of the hand.
Explain the role of the C7 nerve?
C7 controls the triceps. The C7 dermatome goes from the shoulder down the back of the arm and into the middle finger.
Explain the role of the C8 nerve?
C8 controls the hands. The C8 dermatome covers the lower part of the shoulder and goes down the arm into the pinky side of the hand.
