Nervous System Flashcards
What does the central nervous system (CNS) feed to?
The spinal cord and the brain
What does the peripheral nervous system (PNS) feed to?
Sensory pathways and motor pathways
What do motor pathways feed to? Describe each one.
Somatic nervous system (you can control it) and the autonomic nervous system (your body does it)
What doe the autonomic nervous system feed to? Describe each one
Sympathetic nervous system (speeds up reactions - epinephrine) and the parasympathetic nervous system (slows down the body’s response - decreases breathing rate
Describe the function of dendrites
It receives nerve impulses from other neutrons or sensory receptors and relays the impulse to the cell body
Describe the function of the cell body
It has the nucleus and is the site of the cells metabolic reactions
It processes the input from the dendrites
Describe the function of the nucleus
Its the control centre for the neuron cell
Describe the function of the axon
Conducts impulses away from the cell body
Describe the function of the axon terminals
They branch out from the axon and release chemical signals to communicate with effectors (neuron, glands, muscles)
Describe the function of the myelin sheath
It increases speed or nerve impulse transmission. It has a fatting insulating layer to protect against charge loss. It also has a glistening white appearance
Describe the function of the schwann cells
Type of glial which is a supporting cell. It forms myelin by wrapping around the axon
Describe the function of the Nodes of Ranvier
They are gaps between the sections of the myelin sheath that function to speed up nerve impulse transmission. It allows the nerve impulse to “jump” from node to node - this is called: Salvatory Conduction
Describe the function of the Neurilemma
It is the delicate membranes supporting the axon of some neurons. It promotes nerve regeneration (the neuron repairs itself)
Myelinated Neurons: speed, covering, neurilemma, colour and system its found in
Increased speed, covering present, neurilemma present, white and PNS
Unmyelinated Neurons: speed, covering, neurilemma, colour and system its found in
Decreased speed, covering absent, neurilemma absent, grey and CNS
What is Demyelinating Disease?
Multiple Sclerosis (MS): something in the body attacks the myelin and it becomes difficult to control movement
Describe the function of the sensory receptors
Receive stimuli and form a nerve impulse
Describe the function of the sensory neurons
Transmit impulses from the sensory receptors to the interneurons
Describe the function of the interneurons
Are found in the brain and spinal cord and they act as an integration centre
Describe the function of motor neurons
Transmit information from the central nervous system to the muscles, gland and other organs
Describe the function of the effectors
Muscles, glands and other organs that respond to impulses from the motor neurons
Construct a reflex pathway for a pin prick to the finger
Stimulus (pin prick) -> sensory receptor -> sensory neuron -> interneuron -> spinal cord -> motor neuron -> effector (muscle) -> response (move finger away)
What is the first step of Action Potential?
Resting membrane potential:
More potassium leaks out than salt is diffusing in
Na/K pump maintains the negative value of about -70mV
What is the second step of Action Potential?
Threshold:
Stimulation causes NA channels to open and NA moves in the cells (it flows down it’s concentration gradient)
Cell becomes more positive inside (depolarization) and it reaches the threshold to stimulate an action potential
What is the third step of Action Potential?
Depolarization:
More NA channels open and NA rushes into the cell
Inside the neuron cell becomes more positive
Na channels shut
What is the fourth step of Action Potential?
Repolarization:
K channels open and K moves out of the cell
The membrane potential returns to resting level and is repolarized
The outside of the axon is positive and the inside is negative
What is the fifth step of Action Potential?
Hyperpolarization:
The cell membrane becomes more negative than the resting potential
This overshoot is caused by the K channels are still open
NA/K pump must now re-establsih ion concentration gradients
What is threshold potential?
A minimum voltage requirement of usually 15m V is required to cause an action potential. Once it gets it started it can have a bigger voltage but will not increase or decrease the action potential
What is an all or none response?
An action potential occurs maximally or they do not occur at all.
Once the threshold is reached you get an action potential
How do humans/ animals detect the intensity of a stimulus if the action potentials are all or none?
By the frequency of nerve impulses (increased stimulus, increased nerve impulses)
And by the number of neurons stimulated (increased stimulus, increased neurons)
What is the refractory period?
When the NA gates are close and the neuron is unresponsive. Because the NA gates are closed Na cannot get into the axon for depolarization to occur.
What is a synapse between a motor neurone and a muscle cell called?
A neuromuscular junction
What is the first step in transmitting the action potential?
Action potentials arrives at the presynaptic cell (axon terminals)
What is the second step in transmitting the action potential?
The action potential stimulates calcium gates to open and calcium flows in to the presynaptic cell. The calcium stimulates vesicles
What is the third step in transmitting the action potential?
Vesicles filled with neurotransmitters move to the cell membrane of the presynaptic neutron
What is the fourth step in transmitting the action potential?
Neurotransmitters are released by exocytosis from the vesicles in the synapses cleft
What is the fifth step in transmitting the action potential?
Neurotransmitters diffuse across the synapses
What is the sixth step in transmitting the action potential?
Neurotransmitters bind to its receptor on the postsynaptic membrane
What is the seventh step in transmitting the action potential?
Postsynaptic responses occur; it can be excitatory or inhibitory
What is the excitatory postsynaptic response?
Depolarization: NA enters the cell or K leaves the cell. The cell membrane then becomes more positive
What is the inhibitory postsynaptic response?
Hyperpolarization: K rushes out of the cell. The cell membrane becomes more negative
What is the eighth step in transmitting the action potential?
Breakdown of the neurotransmitter: an enzyme breaks down the transmitters left over
What is the ninth step in transmitting the action potential?
Repute of neurotransmitters: the neurotransmitters are broken apart and are then taken back into the presynaptic neutron and repackaged into a vesicle
Where is Acetylcholine (ACh) found, what does it cause, what breaks it down, what does it break down into?
Is found as a neurotransmitter that crosses a neuromuscular junction, causes depolarization, the enzyme that breaks it down is called cholinesterase (which depolarizes it), and it breaks down into acetyl coA and choline
What are the two main structures of the central nervous system (CNS)?
The spinal cord and brain
What matter (colour) is on the spinal cord?
White on the outside and grey on the inside (butterfly)
What matter (colour) is on the brain?
Grey on the outside and white on the inside
What protects the spinal cord?
The vertebrae/ spinal column and cerebrospinal fluid (CFS)
What protects the brain?
The skull, blood brain barrier and the CSF
What is the function of the cerebellum?
It controls unconscious posture reflexes and motor skills
What is the function of the medulla oblongata?
It controls automatic involuntary responses (breathing, heart rate etc)
What is the function of the pons?
It is the relay centre between the neurons of the rights and left halves of the cerebrum
What is the function of the midbrain?
Relays visual and auditory information, controls eye movement, skeletal muscles
What is the function of the thalamus?
Relay station for the forebrain and the hindbrain, relays all senses except smell
What is the function of the hypothalamus?
Releasing hormones to stimulate other glands
What is the function of the cerebrum?
Centre for intellect, memory, consciousness, language and interprets the response to sensory information
What is the function of the frontal lobes?
Motor cortex, smell, relay centre, and thinking
What is the function of the temporal lobes?
Auditory reception, understanding speech and retrieving verbal and visual memories
What is the function of the parietal lobes?
Touch, taste, temperature awareness (TTT), body positioning
What is the function of the occipital lobes?
Receive and analyze visual information
What is the function of the optic nerve?
Transmits sensory information to the brain
What is the function of the vitreous humour?
Jelly like – Supports the eye ball with the pressure of the fluids it contains
What is the function of the sclera?
Protects and supports the eyeball
What is the function of the retina?
Rods: Photoreceptors that are sensitive to dim lights
Cones: Photoreceptors that are sensitive to different wavelengths of light (colour vision)
What is the function of the blind spot?
A point that contains no photoreceptors
What is the function of the fovea?
Contains a high density of cones and provides acute vision.
What is the function of the lens?
Focus light rays onto the fovea
What is the function of the ciliary muscle?
Changes the shape of the lens in order to focus
What is the function of suspension ligaments?
Assists the ciliary muscle in changing the shape of the lens during accommodation
What is the function of the aqueous humour?
Maintains the shape of the cornea with oxygen and nutrients
What is the function of the iris?
Regulates the amount of light that enters the eye. Part of the pupillary light reflex
What is the function of the pupil?
Opening for light to enter the eye
What is the function of the cornea?
Bends light rays into the eye
