bio exam

what are the 2 parts of the nervous system?

1. central nervous system(CNS)
2. peripheral nervous system(PNS)

what does the central nervous system consist of?

-brain
-spinal cord

what is the peripheral nervous system made up of?

-nerves(bundles of nerve cells) that carry information to and from the CNS

what are the cranial nerves?

-connected to the brain
-12 pairs

what are the spinal nerves?

-connected to the spinal cord
-31 pairs

what are the two types of nerves?

-sensory nerves
-motor nerves

what do sensory nerves do?

-carry information from receptors to the CNS

what are mixed nerves?

-they are made up of both sensory and motor fibers
-carry impulses both to and from the CNS

what are interneurons? (3)

-associative neurons
-relay impulses from one neuron to another in the brain and spinal cord(CNS)
-most neurons in the human nervous system are interneurons

what do motor nerves do?

-carry information from the CNS to effectors(muscles+glands)

what is a resting neuron?

-a neuron that is not in the process of transmitting a nerve impulse

what charge does the inside of the cell membrane of a resting neuron have?

-negative

what charge does the outside of the cell membrane of a resting neuron have?

-positive

what does it mean when the cell membrane of a resting neuron is polarized?

-negative charge on the inside and positive charge on the outside

what ions take part in the polarization of a nerve cell membrane?

-mainly sodium and potassium ions(both have a positive electrical charge)

what is the sodium-pottasium pump?

-the nerve cell membrane pumps sodium ions out of the cell and potassium ions into the cell by means of active transport
-the active transport mechanism that performs this pumping action is called the sodium-pottasium pump

where does stimulation of a neuron begin?

-at it's dendrites

what happens when a dendrite is stimulated?

-it becomes depolarized(positively charged on the inside of the cell membrane and negatively charged on the outside of the cell membrane)
-after a depolarization passes part of a neuron, the cell membrane quickly repolarizes

how does a depolarization move throughout the neuron?

-like a wave from dendrites--\>cell body--\>axon--\>synaptic knobs

what are Schwann cells?(4)

-special cells found in the nervous system
-pancake-shaped
-they wrap around the axons of some neurons
-an axon that has Schwann cells wrapped around it is myelinated

what do Schwann cells do?

-they help to transmit nerve impulses faster

What is the difference between a nerve impulse going through myelinated vs unmyelinated axon?

-in non-myelinated cells, nerve impulses move at 2metres per second
-in myelinated cells, nerve impulses move 50x faster at 100 metres per second

what is multiple sclerosis(MS)? what does it do?

-condition in which the immune system attacks and damages the Schwann cells
-this slows down how fast nerve impulses can pass through neuron's which affects a person's ability to move

what are the 4 steps of the transmission of a nerve impulse between neurone at a synapse?

1. a nerve impulse (\= depolarization) reaches the synaptic knob of a neuron

2. this causes several synaptic vesicles to fuse with the cell membrane of the pre-synaptic neuron releasing neurotransmitters into the synapse

3. the neurotransmitters diffuse across the synapse and attach to sodium channels on a dendrite of the post-synaptic neuron

4. this causes the sodium channels to open and allow sodium ions (NA+) to enter the post-synaptic neuron which causes this neuron to become depolarized

what is a neuromuscular junction?

-a special type of synapse between a motor neuron and a muscle cell

do muscle cells contract on their own?

-no, they are told when to contract by motor neurons

what is acetylcholine?

-the neurotransmitter that is used at neuromuscular junctions

what is the neurotransmitter that is used at neuromuscular junctions?

-acetylcholine

what are peripheral neurons?

-the neuron's that have Shwann cells on them
-part of the peripheral nervous system

what are the 3 parts of the human brain?

1. brainstem
2. cerebellum
3. cerebrum

what is the brainstem? what does it control?

-the part of the brain that is attached to the spinal cord
-controls basic physiological functions including breathing, heart rate, blood pressure, sneezing, coughing, swallowing

where is the cerebellum found? what does it do? (3)

-found at the back of the brain
-coordinates voluntary muscle movements
-used for keeping your balance

what is the cerebrum? what does it do/control? (3)

-the biggest part of the brain
-initiation of voluntary movement
-touch, vision, hearing, thought, judgment, reasoning, problem solving, emotions, memory

what is the eye?

-the organ used for vision

the walls of the human eye are made up of how many layers?

-3
-outer layer\=sclera and cornea
-middle layer\=choroid coat
-inner layer\=retina

what is the optic nerve?

-a cranial nerve
-sends visual information from the eye to the brain
-sensory nerve

what is the pupil?

-the black circle in the eye which light enters through

how is the size of the pupil controlled?

-autonomic nervous system
-it has muscles that can make the size of the pupil larger or smaller
-in dim light, the pupil becomes larger to allow more light to enter the eye
-in brighter light, the pupil becomes smaller to let less light into the eye

what is the iris?

-the coloured part of the eye

what is the sclera? what does it do?

-the tough, white outer part of the eye
-helps give the eye shape and protects the inner parts of the eye

what is the cornea? what does it do?

-the transparent layer at the front of the eye
-light enters the eye through the cornea

what is the choroid coat?

-dark brown middle layer
-stops the reflection of light within the eye

what is the retina?

-a layer at the back of the eye that contains nerve cells that are stimulated by light

what does the lens do?

-focuses light entering the eye on the retina

what does the optic nerve do?

-carries nerve impulses from the retina to the brain

what is the ciliary muscle? what does it do?

-a circular ring of muscle that attaches all the way around the lens(holds the lens in place)
-can change the shape of the lens by stretching it at its edges(which allows the eye to focus on objects)

what is the blind spot?

-the region on the retina that contains no rod or cone cells because its where the optic nerve exits the back of the eye

what two cavities is the eye divided into?

1. cavity between the cornea and the lens\=filled with transparent watery fluid called the aqueous humor
2. large cavity behind the lens\=filled with a colourless, jellylike liquid called the vitreous humor(which gives the eye a firm shape)

what is the difference between nearsighted and farsighted?

-nearsighted\=can see objects near them more clearly than far because they have a long-shaped eye
-farsighted\=the lens focuses light from nearby objects at a point beyond the retina which makes close images blurred
-eyeball is too short

what are the light sensitive cells?

-rods
-cones

what are rods?

-sensitive to weak light but not to colour
-allow a person to see in dim light(black and white vision)

what are cones?

-sensitive to colour but must have bright light to function
-3 types\=sensitive to red light, green light and blue light

what is night blindness?

-caused by too little vitamin A
-people with this have trouble seeing in dim light
-the amount of retinal in both rods and cones is decreased so they become less sensitive to light

what is colour blindness?

-an inability to see certain colours
-hereditary condition in which the proteins of one or more of the three types of cones don't work properly

the ability of a cell to respond to its environment is called \_________.

-irritability

what are the two other types of body structures along with nerve cells that carry impulses throughout the body?

-receptors
-effectors

what are receptors?

-sense organs
-specialized structures that are sensitive to certain changes, physical forces, or chemicals both inside and outside the organism

after a receptor is stimulated, the impulses are carried/transmitted to \________?

-an effector

what is an effector?

-a specialized structure that responds to the commands of the nervous system
-either a gland or a muscle
-gland\=nerve impulse will cause it to either increase or decrease its activity
-muscle\=nerve impulse will cause it to contract

what is a stimulus? what does it do?

-anything that causes a receptor to start impulses in a nerve pathway
-it causes electrical and chemical changes in the receptor
-these changes start the nerve impulses

what are the 3 basic events in nervous regulation?

1. a stimulus activates a receptor
2. impulses are started in associated nerve pathways
3. an effector responds to the impulse

what is the brain? what does it do?

-a specialized group of nerve cells
-controls and coordinates the activities of the nervous system

what 2 types of impulses can neurons send?

-electrical
-chemical

do nerve impulses pass through the cytoplasm of neurons?

-no, they are transmitted only along the cell membrane

what are the 3 basic parts of a neuron/nerve cell?

-cell body
-dendrites
-axon

what does the cell body contain? what does it do? (3)

-contains the nucleus and the cell organelles
-controls the growth of the nerve cell
-materials that are needed for the maintenance of the nerve cell are made in the cell body

what are the dendrites? what do they do?

-short, highly branched fibers that receive impulses
-they generally conduct impulses towards the cell body

what is the axon? what does it do?

-usually a long, thin fiber that extends from the cell body
-usually carry impulses away from the cell body and send them to either other neurons or to effectors

what is another name for either the axon or dendrite of a neuron?

-nerve fiber

what do Shwann cells produce?

-layers of a white, fatty substance called myelin(which makes an axon with Shwann cells become myelinated)

what are the nodes of Ranvier?

-gaps in the myelin between neighbouring Shwann cells

what is a synapse?

-the place between the terminal branch of a neuron and the membrane of another cell
-impulses are carried across this gap from the axon to the neighbouring cell

each axon may have one or more synapses with as many as \_____________.

-1000 other neurons

what is the refractory period? how long does it last?

-a brief period immediately following the passage of an impulse, in which the nerve cell membrane cannot be stimulated to carry impulses
-a few thousandths of a second

what 2 factors does the rate at which impulses travel depend on?

1. the size of the nerve fiber
2. whether or not it has a myelin covering

why do myelinated fibers carry impulses more quickly? (3)

-the impulse "jumps" from one node of Ranvier(where the axon is bare) to the next
-this is called saltatory conduction
-it is faster and uses less energy

why is myelin important?

-It speeds up signal conduction in the nerve fiber
-It is formed to assist in the regeneration of damaged fibers
-It insulates the nerve fiber

what is threshold?

-the minimum level of sensitivity in a nerve cell

what happens if the strength of the stimulus is below the threshold of a nerve cell?

-the stimulus cannot start impulses in the neuron

what is the same in all impulses?

-they are all the same size
-the pass along the neuron at the same rate

what 2 things is the strength of a stimulus measured by?

1. a stronger stimulus causes more impulses to be transmitted each second(the impulses follow each other more closely)
2. different neurons have different thresholds(some need a stronger stimulus than others to transmit an impulse)

what is the synaptic gap?

-the narrow space between the synaptic know and the neighbouring cell

what does the synaptic knob contain?

-many small sacs(synaptic vesicles) that contain special chemicals called neurotransmitters

what are excitatory neurotransmitters?

-these chemicals start impulses in their neighbouring neurons

what are inhibitory neurotransmitters?

-these neurons release neurotransmitters that inhibit/block that start of impulses in neighbouring neurons

what do the axons of motor neurons end in?

-motor end plates(they contain neurotransmitters)

what does acetylcholine do?

-causes muscles to contract

what poisons can cause muscle paralysis? why? how can this be fatal?

-nerve gas, botulin, toxin and some insecticides
-they interfere with the functioning of acetylcholine at neuromuscular junctions
-if the muscles of the respiratory system become paralyzed, you will die

what are stimulants?

-drugs that speed up the body's activity
-overuse can cause heart attacks and other problems

what are amphetamines? (3)

-"uppers"
-drugs that produce their effects by binding to certain receptors
-causes short-lived feelings of well being and excitement, followed by depression

what are barbiturates?

-"downers"
-drugs that produce a depressant effect by blocking the formation of norepinephrine

what are LSD("acid") and mescaline?

-mind-altering or hallucinatory drugs
-interfere with the effect of serotonin, an inhibitory transmitter

what are the 2 sensory functions of the ear?

-hearing
-helping to keep balance or equilibrium

what are the 3 parts of the ear?

-outer ear
-middle ear
-inner ear

what does the outer ear consist of?

-pinna
-a short auditory canal

what is the pinna? what does it do?

-a flap of skin supported by cartilage
-mainly functions as a collecting funner for sound waves

what is found along the auditory canal?

-special glands that secrete a waxy material
-this wax prevents foreign objects from entering the ear

what is the tympanic membrane?

-eardrum
-stretches across the inner end of the auditory canal

what is the middle ear filled with? where does the middle ear begin?

-filled with air
-begins at the eardrum

what 3 tiny bones does the middle ear contain? what do they do? (3)

-hammer, anvil, stirrup
-they form a chain across the middle ear that links the eardrum to another membrane(the oval window)
-the hammer is attached to the eardrum, the anvil connects the hammer to the stirrup, and the stirrup is connected to the oval window