26-29 Flashcards
Neuron
Is the basic unit of the nervous system, is a nerve cell that transmits a message from one part of the body to another
Dendrite
Receives message and transmits towards the cell body of the axon
Axon
Transmits messages to axon terminal
Axon terminal
Passed message on to next neuron
Glial Cells
Nourish neurons, remove their wastes and defend against infection
Myelin Sheath
Insulates, protects, and nourishes the axon. Leads to faster conduction of nerve impulses. Made of shwaan Cells
Nodes of ranvier
Saltatory conduction
Nerves
Bundle of axons enclosed within a connective tissue sheath, they permit long distance communication between the brain or spinal cord and the rest of the body
Resting Potential
When a neuron is not being used. Membrane pumps Na ions outside the cell and K ions inside the cell. Outside the cell is positive and inside is negative, the charge difference in the neuron means it is polarized
Action Potential
Occurs when a neuron is stimulated sufficiently, na channels in the membrane open up. Na rushes into the cell by diffusion, other Na channels open up (positive feedback). Impulse travel down the length of the neuron
Repolarization
Needs to occur for the neuron to be stimulated again (must return to resting potential), after Na channels open the K channels open and K Ions flood out causing the membrane potential to become negative again
Refractory Period
Even though the neuron is at resting potential, it cannot be stimulated because Na is on the inside and K is on the ground outside, Na and K membrane pumps are exchanging Na for K without potential changing to allow it to be stimulated again
All or nothing theory
All action potentials are the same magnitude, neither stronger nor weaker than another. If stimulation is below threshold level no action potential occurs, if it is above threshold level, then cell is always depolarizer to the same level
Saltatory Conduction
The action potential moves along nerve membrane differently in myelinated vs unmyelinated nerve cells. Myelinated cell Potential jumps from one node of ranvier to another, very fast
The synapse
Action potential arrives here, and a neurotransmitter is released from pressynaptic vesicles. Neurotransmitter (ACH and norepinephrine) diffuses across cleft and binds to receptors on Na channels, causes action potential in post synaptic neuron. Ach-are secreted to break ACH into inactive fragments, allowing the second neuron to reset
Summation
If the summed effect if excitory impulses is greater than inhibitory impulses then the membrane will depolarize, if threshold is reached =action potential
Excitory synapse
Occurs when neurotransmitter depolarize postsynaptic membrane- making it more likely to have an action potential
Inhibitory Synapse
Occurs when neurotransmitter reduces ability of postsynaptic membrane to depolarize making it less likely to have an action potential
Neuromuscular Junction
Synapses between neurons and skeletal muscles, ACH is the chemical transmitter. Depolarizes muscle cell membrane, causes muscle contraction
Reflexes
Use very few neurons to transmit messages so they are very fast, does not involve the brain
Sensory neurons
Receive information and transmits it to the central nervous system
Association neurons (interneurons)
Located in the central nervous system
Motor neurons
Transmits message from central nervous system to muscle
Steps in reflex arc
- Sensory cell receptor recognizes stimulus
- Sensory neuron carries impulse to the CNS
- Association neuron in CNS selects the appropriate response
- Motor neuron carries the impulse back to the appropriate muscle or gland
- Effector carries out the command
Structures in the CNS
Consists of the brain and spinal cord
Structure of the peripheral system
Consists of all nerves lying outside of the central nervous system
Medulla Oblongata
Involuntary control, heartbeat, blood pressure, rate and depth of breathing
Hypothalamus
Regulation of body temp, control of hunger, production of hormones, regulation of water and electrolytic balance
Thalamus
Central relay system for sensory impulse, channels sensory impulses to appropriate regions, all regions of cerebral cortex communicate with the thalamus
Cerebellum
Controls coordinated muscular activity below the level of conscious
Pons
Is a relay between the cerebellum and the cerebral cortex
Cerebrum
Conscious part of the brain, divided into left and right hemisphere, and has for lobes
Frontal Lobe
Motor areas: voluntary skeletal movement, contains Broca’s area
Association areas: higher mental processes, problem solving and reasoning, personality, logic
Broca’s area
Coordinates muscles for speech and translates thoughts into speech
Parietal Lobe
Sensory areas:
Sensations of touch, pressure, pain, and taste
Temperature
Process information about body’s position and orientation
Temporal lobe
Responsible for hearing, contains wernickes area (stores the information involved in language comprehension)
Occipital Lobe
Responsible for vision (receiving and analyzing), recognition of what is being seen
Protecting the Brain
- Hard skull surrounds the brain
- 3 meninges surround the brain (dura mater, pia mater, and arachnoid)=tough protective membranes
- Blood brain barrier: toxins in the blood can damage brain tissue, blood is not permitted to touch the brain. Brain is nourished by cerebrospinal fluid, nutrients diffuse into the CSF
Spinal Cord
Consists of 31 segments each giving rise to a pair of nerves, white matter lies external to gray matter.
2 functions: centre of simple spinal reflexes, connects peripheral nerves to the CNS
Peripheral Nervous System
Sensory Somatic: voluntary systems both sensory and motor
Autonomic: involuntary systems that you are not aware of (sympathetic or parasympathetic)
Sympathetic: effects
Flight or fight response, increase heart rate and blood pressure, dilate pupils, increases rate and depth of breathing, decreases peristaltic action, uses norepinephrine
*tend to be excitatory and get body to deal with an emergency situation
Parasympathetic Effects
Rest and digest response, lowers heart rate and blood pressure, constricts pupils, increases peristaltic action, acetylcholine
*counteracts sympathetic ns, returns the body to normal after an emergency as passed
Receptors
Are stimulated by external stimuli and they stimulate sensory neurons which send messages to the brain for interpretation, are grouped according to kind of stimulus they receive
Photoreceptor
Respond to visible wavelength of light
Ex: sight
Mechanoreceptor
Sensitive to mechanical energy (movement and vibrations)
Ex: ear
Thermoreceptor
Sensitive to heat and cold
Ex: skin
Osmoreceptor
Detect changes in the concentration of solutes in body fluids
Chemoreceptor
Sensitive to specific chemicals such as the concentration of oxygen in the blood
Ex: smell and taste
Nociceptor
A pain receptor that is sensitive to tissue damage
Sensory adaptation
When a receptor becomes accustomed to a stimulus and ceases to fire, even though the stimulus is still present
Sclera
A tough, protective layer that surrounds the eyeball. The front of the sclera is transparent and is called the cornea
Choroid
Located just inside the sclera, this layer contains blood vessels that nourish the eye. Toward the front of the eye, forms the iris and ciliary muscles that can control the shape of the lens
Retina
The innermost layer, layer contains photoreceptive cells called rods and cones which transmit visual information to the brain via the optic nerve
Pupil
Is a hole that can be made bigger or smaller by the action of the muscular iris. Under low light conditions, the pupil gets bigger to let more light in. Under high light conditions the pupil gets smaller to control the amount of light entering the eye. (Accommodation)
Vision
Light first passes through the cornea and then a liquid called the aqueous humour before it passes through the pupil, aqueous humour is responsible for maintaining the shape between the lens and the cornea as well as supplying that part of the eyeball with nutrients and oxygen
Lens
Job is to focus the incoming light precisely on to the retina at the back of the eyeball, can change shape
Lens is thicker: can focus light from nearby objects
Lens is thinner: can focus light from distant objects
Lens and convexity
As a viewed object becomes closer, convexity of the lens increases
As a viewed object becomes more distant, the convexity of the lens decreases
Myopia (nearsightedness)
If the lens is too strong, or your eyeball too long, the image is projected in front of your retina
Hyperopia (farsightedness)
If the lens is too weak, or your eyeball too short the image is projected behind your retina
Cones
Respond to colours, mostly concentrated around the centre of your retina, in a spot called the fovea centralis. Not found in the periphery of the eyeball, 3 kinds of cones (red, blue, or green) lead to the perception of different colours
Rods
These are sensitive to light and are responsible for black and white vision under low light conditions, found more on the periphery of the eyeball than cones
Blind spot
Spot where the optic nerve connects to the retina and has no rods or cones
Chemistry of Vision (Rods)
Rods contain a chemical called rhodopsin. When light strikes a rod, rhodopsin is split which changes the membrane permeability of the rod and causes an action potential
Chemistry of Vision (cones)
Cones contain a chemical called photopsin, each type of cone has a specific photopsin that will split only when stimulated by a certain colour wavelength
Photoreception
Once rods and cones are stimulated they send a neural message to the occipital lobe of the brain, which processes and integrates the information and then perceives it as an image
Colour blindness
A lack of one of the three types of cones (usually red or green), people find it difficult to distinguish between these 2 colours
Astigmatism
An uneven curvature of the eyeball that leads to unequal focus of some parts of your field of view
Cataracts
Proteins in the eye begin to degenerate making the lens opaque
Pinna (outer ear)
Collects sound
Auditory canal (outer ear)
Carries sound to eardrum
Tympanic membrane (middle ear)
Eardrum
Ossicles (middle ear)
Hammer, anvil, and stirrup
Oval window (middle ear)
Connects to cochlea
Eustachian tube (middle ear)
Equalizes air pressure
Vestibule (inner ear)
Contains utricle and saccule which detects head position
Semicircular canals (inner ear)
Contains hair cells which respond to body movement
Cochlea (inner ear)
Made up of organ of corti and basilar membrane which sends impulses to the brain via the auditory nerve in response to sound
How we Hear
- Pinna helps funnel sound into the auditory canal
- Auditory canal transmits sound to the tympanic membrane and makes it vibrate
- Vibration of the eardrum is picked up and amplified by the ossicles, these transmit vibrations to the oval window of the cochlea
Cochlea
Consists of 3 fluid filled chambers, middle chamber contains the organ of corti which is the actual structure responsible for hearing
Hearing vibrations
Vibrations of the ossicles cause the oval window to oscillate, creates waves in the fluid filled upper chamber, the waves travel the length of the upper chamber then enter the lower chamber until they hit the round window
Organ of corti
Has a basilar membrane (bottom) and tectorial membrane (top) connected by hair cells. Waves in fluid of the other 2 chambers cause basilar membrane to move up and down, as it does hair cells push against tectorial membrane and they bend. Leads to depolarization of hair cells which are transmitted to the brain causing perception of sound
Hearing loss
Result of nerve damage (damage to hair cells), or damage to sound conduction components of the ear (tympanum or ossicles).
Repeated loud noises damage hair cells
Conduction deafness is treated by hearing aids
Gravitational Equilibrium
Head position, is detected by the utricle and saccule
Rotational Equilibrium
Movement, is detected by the semi circular canals
Detecting Movement
Each semicircular canal has a bulge at the base called an ampulla, within is a cupula. When you are moving fluid in the canal moves against the hair cells in cupula causing them to depolarize and begin an action potential, arranged in different planes to detect movement in different planes
Head position
Utricle and saccule contain tiny hair cells suspended in jelly like material, contains small pieces of calcium carbonate (otoliths), when our head is tilted forward otoliths shit because of gravity which causes jelly like material to shift and the cilia on hair cells to bend. Cause depolarization and an action potential
Proprioceptors
Found in muscles, tendons and joints and provide information about body position to the brain
Ex: you know if your arm is bent even if your eyes are closed
Taste
Tongue contains chemoreceptors called taste buds
4 kinds of receptor cells: correspond to 4 basic tastes (sour, sweet, salty, and bitter)
Perception of taste is a result of information received from the tongue as well as the nose, sent to the parietal lobe of the brain
Smell
Olfactory cells are chemoreceptors, different chemicals in the air stimulate olfactory cells and trigger an action potential
