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Bio 30/ 26-29
Transcript of Bio 30/ 26-29
Cell body (soma)
Branching Dendrites: short, branching terminals that receive nerve impulses. Branchings: ends of the axon. Myelin sheath: a fatty insulating layer that surrounds some axons. It's purpose is to protect the neuron and to speed up the rate of nerve impulses. Axon is said to be myelinated or unmyelinated. Schwann cells: a form of glial cell that forms myelin in axons. White matter: is formed by myelinated axons.
Grey matter: is formed by unmyelinated axons. Cell body: contains the cell nucleus and is the site of the cell's metabolic reactions. It process input from dendrites. Axon: conducts impulses away from the cell body. It can end in a gland or a muscle, but it can also end in another neuron. Action potential Membrane potential: the charge separation across and axon membrane. Resting membrane potential: -70 mv in unstimulated neurons. It is negative in the inside and positive in the out side. Polarization: the process of generating a resting membrane of -70mv. * Negatively charged proteins molecules are too large to cross through the membrane, so they stay in the intracellular fluid and create the negatively charged inside of the neuron. Sodium-Potassium pump: are special pumps that move 3Na to the outside of the axon and 2K into the axon. This creates a high concentration of Na outside of the axon and a low concentration of K inside of the axon. axon high K low K high Na low Na +++++++++++++++++++++++++++ ------------------------------------------ Step one: when the an stimuli makes the membrane potential reach above (more positive) its threshold of -55. This is called the depolarization. When this happens, voltage gated sodium channels will allow Na+ to rush into the membrane and, therefore, changing the negative potential of -75 to a positive of about +30.
Step two: When the action potential is reached (+30), then the voltage gated potassium channels will allow K+ to flow out from the axon to the outside because of its concentration of gradient. This makes the axon negative. This is called repolarization. Hyperpolarization: it occurs when the repolarization passes its normal -75mv to a more negative one, most likely -90mv. Refactory period: the time where the membrane in a part of a axon cannot undergo another action potential. This prevents the signal from going backwards. Impulse: is the action potential moving from nodes of Ranvier to the next until it reaches the axon's terminal point. Synapse: is the connection between two neurons or between a neuron and an effector Synapse Neuron junction: a synapse between a motor neuron and a muscle cell. Synaptic terminal: the end of the axon. Synaptic cleft: the gap between two neurons. Presynapticneuron: the neuron that sends the signal to the next neuron. Postsynapticneuron: the neuron that receives the signal. Neuron transmitter: chemical messenger that carries the neural signal (information) from one neuron to the other. Neurontransmitter synaptic vesicles: when the information arrives at the synaptic terminal, the impulse causes sacs to in the presynaptic neuron to release te neurontransmitters from inside of them. Acetylcholine: is a neurontransmitter that is involved in the synapse of neuromuscular junction (neuron to muscle). Cholinesterase: an enzyme that breaks down acetylcholine. Excitory: when the neurontransmitters trigger the receptors to allow positively ions, Na+, to flow into the postsynaptic neuron in order to make depolarize, and therefore, continue the to pass on the signal. Inhibitory: when the neuron transmitters stimulate the receptors to allow potassium ions to flow in to the postsynaptic neuron. spinal cord Grey matter= unmylinated axons
white matter= mylinated axons The brain is divided into three main parts. Forebrain Hindbrain Midbrain Thalamus
Pons It relays visual and auditory information between hindbrain and forebrain. Meninges: the three layers that protect the brain and spinal cord. Blood-brain barrier: the separation of blood from the brain the spinal cord's cells. Glucose and oxygen pass through the barrier by special transport mechanism. Lipid-soluble substances such as alcohol can easily pass through the barrier. Cerebrospinal fluid: a fluid between spaces in the brain and spinal cord. About 150ml and is change 4 times a day. Cerebral hemisphere: the right and left sides of the cerebrum Corpus callosum: the bundle of white matter that links the right and left cerebral hemispheres. The four lobes of the brain Frontal lobe: conscios thoughts, movements and speech.
Pariental lobe: touch and taste.
Temporal lobe: hearing and speech
Occipital lobe: vision Sensory receptors Photoreceptors: rods and cones in the eye (stimulated by light).
Chemoreceptors: are stimulated by certain chemicals (nose and tongue).
Mechanoreceptors: stimulated by mechanical forces from some form of pressure (hearing sensors and balance sensors).
Thermoreceptors: detect heat and cold (skin recetors). Sensation: occurs when the neural impulses arrive at the cerebral cortex. Perception: how the cerebral cortex interprets the meaning of sensory information. Brain Spinal cord Brain and Eye The ear Sclera: is a protective layer.
Cornea: helps to bend the light coming into the eye.
choroid: intermediate layer that supplies the retina with nutrients.
Iris: regulates the amount of light that enters the eye.
Pupil: is the opening where light enters the eye. Internal layer (retina) Rods: photoreceptors that are sensitive to dim light.
Cones: photoreceptors that are sensitive to wavelengths (colour light).
Fovea centrails: contains a high density of cones. Lens: focuses light into the fovea centrails Aquous humour: which maintains the shape of the cornea.
Vitrous humour: which maintains the shape of the eye ball. Humour Focussing... To see a far object the ciliary muscles relax and the suspensory ligaments become taut, which makes the lens "flattened." To see near objects the lens becomes round because the ciliary muscles become taut and the suspensory muscle become relax. Accommodation: is the ability of the lens to change shape in order to focus better on an object. Cataracts: is a condition caused by the degeneration of the protein structure, which makes the opaque and prevents light from passing through (caused by age). Astigmatism: uneven curvature of part pf the cornea. Myopia: when the eyeball is shaped long and the light focus in front of the retina. People with this condition cannot see far objects. Hyperopia: in this condition the eyeball is too short and the light focus behind the retina. People with this condition cannot see near objects. Pods and cones *70% of Human receptors are found in the eye. Rods contain light absorbing pigment called rhodosin
Cones contain the pigment photopsin. When light stimulates these pigments, it causes a chain reaction that stops the release of the inhibitory neurotransmitter. Outer ear Pinna-outside flap of the ear. It enhances sound vibration and focuses them into the ear.
Auditory canal-tube that leads to the eardrum. Middle ear Tympanum- (ear drum) is a round elastic structure that vibrates in respond to sound waves.
Ossicles- three tiny, interconnected bones. They are the smallest bones found in the human body and their purpose is to amplify sound.
Oval window- where the ossicles concentrate the vibrations.
Eustachian tube- is connected to the throat and its purpose is to equalize the air pressure within and outside of the middle ear. Inner ear Cochlea-"snail" shape structure that is the site where mechanical impulses are transmitted to the brain.
Organ of Corti- is found in the cochlea and is also known as the organ of hearing.
Basilar membrane- is the base of the organ of corti and is where hair cells are located.
Tectorial membrane- this membrane has stereocilia, which are tiny projections that stick out from the cells. Pressure moves the liquid inside the cochlea and causes the hair cells to bend the tectorial membrane. The hair cells then synapse with nerve fibres of the auditory nerve, which then sends this information to the brain. Semicircular canals, Utricle and Saccule Semicircular canals contain mechanoreceotors that detect head and body rotation (rotational equilibrium). Utricle and Saccule: they make up the fluid-filled vestibule of the inner ear. They keep the body's balance (gravitational equilibrium). Cupula: Jelly-like fluid that covers the steriocilia of hair cells. Otoliths: calcium carbonate granule found in utricle and saccule canals and their purpose is to move the hair cells. The otoliths are on top of a jelly-like fluid where the hair cells are embadded. Proprioceptors: are another kind of mechanoreceptors involved in coordination. They are found in the muscles, tendons and joints. Smell Olfactory cells: are chemoreceptors in the nose that are stimulated by chemicals that enters the nose. *Smell and taste are related. The tongue can only distinguish between sweet, sour, salty, and bitter. The other flavors that we taste, which are around 90%, come from smell. Pain: when tissue is damaged, cells called nociceptors release chemicals that trigger pain receptors to send a impulse to the brain.