Nervous System Flashcards
What are the two main divisions of the nervous system?
Central Nervous System (CNS)
Peripheral Nervous System (PNS)
What are neurons?
Conducting cells
Transmit nerve impulses
Are bundled into tissues called nerves in the PNS and tracts in the CNS
What are glial cells?
The glial cells surround neurons and provide support for and insulation between between them
They are the most abundant cell type in the CNS
Schwann cells are a type of glial cell
What are the three types of neurons?
Sensory neurons
Interneurons
Motor neurons
What do sensory neurons do?
Gather information from the sensory receptors (senses) and transmit these impulses to the CNS
What do interneurons do?
Only I’m the CNS, they are the link between the sensory and motor neurons, they process incoming sensory information and relay to motor neurons
What do motor neurons do?
Transmit info from the CNS to the muscles, glands, and other organs
What are the parts of a neuron? (7)
Dendrites Cell Body (Soma) Axon Myelin Sheath Schwann Cells Nodes of Ranvier Neurilemma
What are dendrites in a neuron?
Receive information from receptors or other neurons
What is the cell body (soma) in a neuron?
Contains nucleus and other organelles
What is the axon in a neuron?
Longest cytoplasmic extension from the cell body
What is the myelin sheath in a neuron?
Made up of fatty protein and acts as insulation/protection and speeds up nerve impulse
What are Schwann cells in the neuron?
They are part of the myelin sheath and are wrapped around the axons
What is the difference between white matter and gray matter?
White matter has Schwann cells that produce myelin sheath
Gray matter is unmyelinated
What are the nodes of ranvier in the neuron?
Areas between sections of myelin
Impulse jumps from one node to another, speeding up impulse transmission
What is neurilemma in neurons?
Only present on some neurons (PNS mostly)
Allows for regeneration after damage
Not on neurons in gray matter (CNS) therefore damage is permanent
What is an action potential?
A temporary shift (from negative to positive) in the neurons membrane
It’s caused by ions suddenly flowing in and out of the neuron
Gated sodium and potassium channels open once an action potential has been triggered
These gates open and closes depending on the voltage difference across the cell
What is resting potential?
It is negative inside (-70 mV)
There is lots of sodium ions outside the cell
This is a polarized state
A sodium-potassium pump maintains this by pumping 3 sodium out for every 2 potassium in
What is depolarization?
Makes the cell less polar
A stimulus causes the polarity to change, sodium gates open and sodium rushes in
The intercellular fluid goes from -70 mV to +40 mV
Before an impulse is generated the threshold potential must be reached
What is repolarization?
The neuron must be returned to its original polarity
The sodium gates snap shut, stopping the inward rush of positive ions. At the same time the potassium gates open, letting potassium into the cell
More potassium in the cell means the cell loses positively charged ions and returns back towards resting state
What is hyperpolarization?
Makes the cell more negative than its typical resting membrane potential
The potassium gates take a really long time to shut and continue to let potassium in
This means the cell temporarily hyperpolarizes or gets more negative than its resting state (-95 mV)
As the potassium channels shut, the sodium-potassium pump works to re-establish the resting state
What is the refractory period?
During this time it is impossible to send another action potential
The sodium gates snap shut, inhibiting sodium from entering the neuron, which would start an action potential
What is the threshold level?
If depolarization reaches the threshold level it triggers the action potential
If it doesn’t reach that point, then the neuron remains at rest
What is an all-or-none response?
Action potential are an all or none response
This means that an action potential is either triggered or it isn’t, like flipping a switch
A neuron will always send the same size action potential
What is a synapse?
How neurons “talk” to each other
The point of communication between two neurons or between a neuron and a target cell
What are the four actions that occur in a synapse?
- Action potential arrives
- Vesicle fuses with plasma membrane
- Neurotransmitter is released into synaptic cleft
- Neurotransmitter binds to receptor
Describe the effects of excitatory neurotransmitters.
Trigger ion channels
Sodium and calcium can enter the cell
Results in more positive membrane potential
If excitatory signals are strong enough an action potential can occur
Describe the effects of inhibitory neurotransmitters.
Trigger potassium channels to open
Potassium flows out of cell
Results in a more negative transmembrane potential (hyperpolarization)
Because the cell is in hyperpolarization it cannot have an action potential (refractory period)
What is temporal summation?
Occurs when multiple signals from one neuron occur close enough in time to combine and trigger an action potential
What is spatial summation?
The effect of triggering an action potential in a neuron from one or more presynaptic neurons
What does the neurotransmitter acetylcholine do?
It’s an excitatory neurotransmitter at neuromuscular junction
Can be either excitatory or inhibitory in other places
What does the neurotransmitter cholinesterase do?
An enzyme that breaks down acetylcholine
Removes acetylcholine from receptors to allow the membrane to repolarize
What does the neurotransmitter norepinephrine do?
Can be either inhibitory or excitatory
Found in both the CNS and PNS
Causes wakefulness
What does the neurotransmitter GABA (gamma-aminobutyric acid) do?
It causes an inhibitory response
Found in the CNS
Associated with motor behaviour
What is the function of the meninges in the brain?
Membranes that protect the brain
Surround the brain and spinal cord
What is the function of the cerebrospinal fluid in the brain?
Is the “shock absorber”
Circulated between the innermost and middle membranes of the brain and spinal cord
What is the function of the cerebrum in the brain?
Muscular control and balance
The largest and most highly developed part of the human brain
Stores sensory information and imitators voluntary motor activities
What is the function of the cerebral cortex in the brain?
The outer layer of the cerebral hemispheres
divided into four lobes
A thin layer of gray matter that makes humans so smart
What is the function of the frontal lobe in the brain?
Control movement of voluntary muscles (walking, speech)
Linked with intelligence, personality, memory, and conscious thought
What is the function of the parietal lobe in the brain?
Associated with touch, temperature, awareness, and body position
linked to emotions and interpreting speech
What is the function of the temporal lobe in the brain?
Associated with auditory reception (hearing)
Linked to memory, and interpretation of sensory information
What is the function of the occipital lobe in the brain?
Associated with vision and interpreting visual information
What is the function of the corpus callousm in the brain?
Links right and left hemispheres
A nerve tract that allows communication between the two cerebral hemispheres
What is the function of the thalamus in the brain?
Receives sensory information from other areas of the nervous system and sends this information to the cerebral cortex
What is the function of the hypothalamus in the brain?
Controls hormones
What is the function of the cerebellum in the brain?
Region of the brain that coordinates muscle movement and balance
What is the function of the pons in the brain?
Relay centres
Acts as a relay system by sending nerve messages between the cerebellum and the hindbrain
What is the function of the medulla oblongata in the brain?
The hindbrain region that joins the spinal cord to the cerebellum
The site of autonomic nerve control
What is the function of the olfactory bulbs in the brain?
Main function is smell
What is the central nervous system?
Brain and spinal cord
Controls most functions of the body and mind
What is peripheral nervous system?
Consists of the nerves and ganglia outside of the brain and spinal cord
The main function is to connect the CNS to the limbs and organs
What are somatic nerves?
Part of the peripheral nervous system associated with the voluntary control of body movements
Consists of afferent nerves (sensory nerves) and efferent nerves (motor nerves)
What are autonomic nerves?
Part of the PNS that control muscles of internal organs and glands
Involuntary nervous system
What is the sympathetic nervous system?
Prepares the body for the “flight of fight” response during any potential danger
What is the parasympathetic nervous system?
Inhibits the body from overworking and restores the body to a calm and composed state
“Rest and digest”
What are the five components of a reflex arc?
- Sensory receptor (affector)
- Sensory neuron (affector)
- Interneuron (spinal cord)
- Motor neuron (efferent)
- Effector (muscle)
What happens during the sensory receptor step in the reflex arc?
Receptor in skin detects a stimulus
Affector neuron
What happens during the sensory neuron step in the reflex arc?
Sends electrical impulses to a relay neuron in the spinal cord
Affector neuron
What happens during the interneuron step in the reflex arc?
Connects sensory neurons to motor neurons
Located in spinal cord
What happens during the motor neuron step in the reflex arc?
Sends electrical impulses to an effector
Efferent neuron
What happens during the effector step in the reflex arc?
Produces a response
In the muscles
What are the three layers of the eye?
Sclera
Choroid
Retina
What is the path of light through the eye?
- Cornea
- Lens
- Retina
- Optic nerve
- Occipital lobe
What is the function of rods in the eye?
Provide vision at low light levels
What is the function of cones in the eye?
Provide vision at a higher light level
Colour vision
What is the function of sclera in the eye?
The white of the eyes
Provides protection and structure
What is the function of the choroid in the eye?
Between the retina and sclera
Has blood vessels for nourishment
What is the function of the retina in the eye?
Photoreceptors
What is the function of the iris in the eye?
Opaque disk of tissue that surrounds the pupil and regulates the amount of light entering the eye
What is the function of the lens in the eye?
Focus the image on the retina
What is the function of the pupil in the eye?
The opening for light to enter the inner eye
What is the function of the fovea cebtralis in the eye?
Contains a high density of cones and provides acute vision
What is the function of the optic nerve in the eye?
Takes messages to the brain
The blind spot of where the optic nerve attaches to the retina
What is the function of the cornea in the eye?
Protects the eye and reflects light toward the pupil
What are the two main functions of the ear?
Hearing
Balance
How does hearing work in the ear?
Sound waves are collected by the outer ear, amplified by the middle ear, and converted to signals in the organ of corti in the inner ear
How does the ear maintain balance?
Controlled by the semicircular canals of the inner ear
What structures are in the outer ear?
Pinna
Auditory Canal
Tympanic Membrane (ear drum)
What structures are in the middle ear?
Ossicle bones
Eustachian tube
What structures are in the inner ear?
Cochlea
Basilar Membrane
Organ of Corti
Semi circular canal
Auditory nerve
What is the function of the pinna in the ear?
To collect sound
What is the function of the tympanic membrane in the ear?
Thin layer of connective tissues that separates the outer and middle ear (ear drum)
What is the function of the auditory canal in the ear?
Transmits sound from the pinna to the ear drum
What is the function of the ossicle bones in the ear?
Job is to amplify the sound waves so they travel through the thicker, fluid filled structures within the inner ear
What is the function of the cochlea in the ear?
Fluid-filled substance containing the basilar membrane and organ of corti
The sites of sound waves converting into electrical impulses that brain can understand
What is the function of the organ of corti in the ear?
Sits above the basilar membrane
Contains hair cells which move and open ion channels
What is the function of the auditory nerve in the ear?
A sensory nerve that transfers auditory information from the cochlea to the brain
What is the function of the semi circular canal in the ear?
Three tiny fluid-filled tubes in the inner ear that helps maintain balance
What is the function of the Eustachian tube in the ear?
Extends from the middle ear to the mouth and nose
Equalizes air pressure
What is the path of a sound wave through the ear?
- Sound waves enter the outer ear and travel through the ear canal to the ear drum
- The eardrum vibrates from the incoming sound waves and sends these vibrations to the ossicle bones
- The ossicle bones amplify the sound vibrations and send them to the cochlea
- Once the vibrations reach the fluid inside the cochlea, a travelling waved forms along the basilar membrane
- Bending causes pore like channels to open up and causes chemicals to rush into the cell, which sends an electrical charge
- The auditory nerve carries this electric signal to the brain which turns it into a sound that we recognize and understand
What are the five types of receptors?
Mechanoreceptors
Photoreceptors
Chemoreceptors
Thermoreceptors
Proprioceptors
What are mechanoreceptors?
Stimulated by pressure (sound or touch)
What are photoreceptors?
Detection of light (photons) we perceive as vision
Two types are rods and cones
What are Chemoreceptors?
Are stimulated by certain chemicals
Two types are olfactory receptors and taste receptors
Olfactory receptors: detect chemical stimuli we perceive as smell
Taste receptors: detect chemical stimuli we perceive as taste
What are thermoreceptors?
In skin, sense hot of cold
What are proprioceptors?
Received stimuli from within the body
Responds to body position and movement
