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Biology 251 study guide

Terms in this set (51)

What is the difference between afferent and efferent neurons?
Afferent neurons travel from the Peripheral NS to CNS. somatic, special and visceral sense are all afferent. transmit information from visceral receptors to CNS, important in maintaining homeostasis
Efferent neurons are output from the CNS to peripheral. somatic and autonomic nervous system
What part of the peripheral nervous syste, controls internal organs by innovating smooth muscle, cardiac muscle, and glands in these organs/tissues?
the autonomic nervous system controls smooths muscles, cardiac muscle, glands, and adipose
Which type of autonomic neurons originates so,we here in the central nervous system? Which type originates in an autonomic ganglion?
preganglionic neurons originate in the ins while post ganglionic neurons grow from the autonomic ganglia
autonomic ganglia
Synapse between pre- and postganglionic neurons occurs in ganglia (collection of neuron cell bodies outside central nervous system)
For both autonomic divisions, list where the preganglionic cell bodies are located within the CNS I.e. brainstem and sacral spinal cord or thoraco-lumbar spinal cord? Do postganglionic neurons form synapses with other neurons or do they synapse with target cells?
1. preganglionic neurons originate in the thoracic and lumbar regions of spinal cord for sympathetic nervous system with short pre to sympathetic chain
2. preganglionic neurons in the parasympathetic originate in brainstem and sacral spinal cord. long pre neurons near effector organ and short post from ganglia to effector organ
Where are the sympathetic ganglia located? Where are the parasympathetic ganglia located?
sympathetic ganglia are located along the spinal cord and parasympathetic ganglia are close or within the organ they belong to
In general, what are the functions of the sympathetic and the parasympathetic divisions of the autonomic nervous system?
sympathetic: fight or flight response, prepare for emergency/stress/ exercise; increase heart rate and bp; mobilize energy stores, pupillary dilation, decrease gastrointestinal/urinary function
parasympathetic: quite, relaxed state, energy conserving, increasingly gastrointestinal activities, decrease HR and BP
What are the autonomic neurotransmitters involved at each different synapse (for both autonomic divisions)?
acetylcholine, epinephrine, norepinephrine
What are the types of adrenergic receptors found in the sympathetic division of autonomic nervous system? In general, which are excitatory and which are inhibitory?
1. alpha 1&2: most common types, found in many different tissues/organs, usually excitatory. affinity greater from norepinephrine then epinephrine
2. beta 1: located primarily in cardiac muscles, usually excitatory, equal affinity for norepinephrine and epinephrine
3. beta 2: located in some blood vessels and smooth muscle, usually inhibitory, greater affinity for epinephrine
4. beta 3: located in adipose tissue, usually excitatory, equal affinity for epi and nore
What are the types of receptors found in the sympathetic division? Where is each type located i.e. on target cells or on post-ganglion cells?
1. nicotinic receptors: also bind and are activated by nicotine, located on post ganglionic neuron cell bodies of both divisions of autonomic n.s.
2. muscarinic receptors: also bind and are activated by muscarine, located on target organs of parasympathetic divisions
Which divisions of the ANS controls the release of epinephrine from the adrenal medulla. Describe the anatomy of then autonomic innervation of the adrenal medulla?
adrenal medulla secrete epi (adrenaline), no post ganglionic axons, controlled by sympathetic nervous system. sympathetic preganglionic neuron goes into adrenal medulla, connects to neurotransmitter on the chromatin cell, episode is secreted from cell into blood vessel
What types of cells do somatic motor neurons control?
control skeletal muscle centers
What is a neuromuscular junction?
synapse between a motor neuron and a muscle fiber
motor end plate
axon terminal plus specialized region of muscle cell membrane
What is the neurotransmitter released at the neuromuscular junction?
action potential in motor neuron triggers release of acetylcholine at neuromuscular junction
The neurotransmitter released at the neuromuscular binds to what type of receptor on the muscular cell membrane?
acetylcholine binds to nicotinic receptors on motor end plate
Describe the events that occur during synaptic transmission at a neuromuscular junction
AP arrive at motor neuron axon terminal. voltage gated calcium channels open. calcium enters cells triggering release of ACh. ACh diffuses across cleft and binds to nicotinic receptors on motor end plate. ACh triggers opening of fast ion channels for small cations- sodium and potassium. net movement of positive charge into muscle cell, depolarization. EPSP causes AP in muscle cell and spreads through muscle causing contraction.
What are the two major types of photoreceptors in the retina
1. Rods: greatest at the periphery; highly sensitive to light, absorb all visible wavelengths of light, more numerous
2. cones: greater near fovea; able to resolve fine detail, each cone absorbs some other wavelengths, but not the same extent
Which of the two types of photoreceptors is responsible for color vision?
cones- there are three types (blue, red, green)
How do the two types of photoreceptors differ with respect to their sensitivity to light vs acuity (I.e. resolution)
rods have low acuity, not able to resolve fine detail
cones have high acuity, able to resolve fine detail
How is light converted to electrical impulses in neurons I.e. photo-transduction?
Photoreceptors release a neurotransmitter that inhibits the bipolar cells and therefore the ganglion cells. When light is absorbed by photoreceptors, no release of inhibitory neurotransmitter. Bipolar and ganglion cells now produce action potentials which travel to visual centers
What is ,want by dark adaptation? Light adaptation?
1. Dark adaptation: exposure to light "bleaches" the photopigment in the rods. Opsin separated from retinal, no more light can be absorbed. Move to dark: sensitivity of rods is low due to previous "bleaching" retinal and opsin re-associate- make new photopigment can again detect light after a few minutes
2. Light adaptation: exposure to dark maintains rods in most sensitive state. Opsin and retinal associated, readily absorb light. Move to bright light sensitive rods overwhelmed, rods begin to be "bleached" not as sensitive again
How is the amount of light entering into the eye regulated? How does the sympathetic nervous system affect pupil diameter?
size of pupil regulates the amount of light entering. iris= smooth muscle (has color pigment) ability to focus light: light waves bend as the pass from one medium density to another -refraction
Which smooth muscles layer in the iris is controlled by the sympathetic nervous system?
outer radial muscle= dilator, makes pupil larger
How does the parasympathetic nervous system affect pupil diameter? Which smooth muscle layer of the iris is controlled by the parasympathetic n.s.
inner circular muscle= constrictor, makes Pupil smaller
Which division Of the ans is involved with focal accommodation in the eyes? What are the changes that occur to the lens to focus a near object?
accommodation: increasing the curvature of the lens to focus light from near objects on the retina. for near vision: leans become rounder due to parasympathetic input
How are sounds Transmitted into the cochlea? What are ossicles of the middle ear and what is their function?
The vibrations pass through the ear drum to middle ear ossicles to amplify sound and back out to cochlea as the vibrations pass through, they go to cochlear duct and over the hair cells that move
Ossicles: tiny bones (malleus, incus, and stapes) that transmit vibrations
How is the cochlea anatomically arranged?
Cochlea consists of 3 chambers, 2 outer are continuous and the one inner is not. The inner chamber has hair cells and basilar membrane.
What is the basilar membrane?
a membrane in the cochlea that bears the organ of Corti.
What is the function of hair cells?
release neurotransmitter that binds to receptors on sensory neurons that deliver information to the brain -> sound perception
How does the cochlea discriminate between sounds of different frequencies?
sound waves per second (hz/s). basliar membrane has areas of hair cells that will maximally vibrate at different frequencies, then send that information to the brain
What is the primary function of each of the following brain regions- hypothalamus, thalamus, cerebellum, cerebrum, brainstem?
Brainstem: controls many involuntary functions like involuntary eye movement
Cerebellum: coordination of body movements, fine control of movement/adjustment of movement
Thalamus: sensory relay to cerebral cortex, all sensory input except olfaction passes through thalamus, some processing of sensory information
Hypothalamus: controls many homeostatic functions (food intake/thirst, thermoregulation, urine output, controls anterior pituitary hormone secretion, coordinated autonomic nervous system
Cerebral cortex (cerebrum): largest region of human brain, anatomically divided into lobes, functional divisions
How is the gray and white matter organized in the spinal cord?
interior is formed in gray matter and surrounded by white matter
what are dorsal and ventral roots of the spinal nerves
ventral: exit pathway for efferent neurons
dorsal: entry pathways for afferent neurons
what type of neuron is found in the dorsal roots? in the ventral roots?
dorsal: sensory neurons
ventral: motor neurons
how is a skeletal muscle cell organized?
Thick and Thin Myofilaments

Sarcomeres

Myofibrils

Skeletal Muscle Cell
what are the two types of contractile filaments?
thick filaments: consist of 2 identical subunits wrapped around each other, one expanded into head region. each head contains both lactic binding sit and an ATPase site
thin filaments: tropomyosin and lactic arranged in a helix formation
what types of proteins make up each of the two filament types and how are they organized?
Thick filaments: consists of many myosin molecules; half are oriented in one direction, half in the other direction, thick filaments attach to titan
Thin filaments: tropomyosin overlaps myosin binding site on actin. Troponin attached to actin/tropomyosin at regular intervals. Each troponin has three subunits: one that binds to actin, one that binds to tropomyosin, and one the reversibly binds to ca2+trigger that starts the contraction, can bind and unbind
what are sarcomeres and how are they organized?
Sarcomeres: functional contractile unit of skeletal muscle, z disk attach to thin filaments, thick filaments in the center and connected to z disk by protein called titin
What are Z disks (Z lines)?
protein disks, a sarcomere extends from z disk to z disk "dinner plate shaped"
What are myofibrils?
bundles of myofilaments that run the length of a fiber
What are Transverse Tubules (T-Tubules)?
invaginations of the sarcolemma that dip into the cell interior at regular intervals. allow AP to travel along sarcolemma and then down to reach sarcomeres
What is the underlying mechanism that allows sarcomeres, and therefore, skeletal muscle cells to shorten?
The cross-bridge cycle pulls the filaments in the sarcomeres closer together causing muscles to contract.
What is meant by the term cross-bridge? What is meant by power stroke?
Cross bridge : connections can form between the thick and thin filaments. Myosin heads (from thick filament) can bind to actin on thin filaments.
Power stroke: myosin heads rotate -> pull thin filaments along thick filaments toward center of the sarcomere
a. Describe the sequence of events that occur during the cross-bridge cycle in skeletal muscle cells.
Myosin heads attach, power stroke occurs, the heads "re-cock" and for another attachment repeating the cycle
what is the role of Ca 2+ in skeletal muscle contraction?
calcium is the signal that ultimately leads to contraction
a. Where does most of the Ca2+ required for contraction come from in skeletal muscle cells? Which protein in a skeletal muscle cell first binds calcium to initiate contraction?
Most of the Ca+ required for contraction come from the sarcoplasmic reticulum and then the calcium binds to actin which regulates skeletal muscle contraction
What is the function of DHP receptors? What is the function of ryanodine receptors
The DHP receptors are voltage sensitive gates that detect an action potential and change shape to open the ryanodine receptors to open
The ryanodine receptors open to release Ca2+ into cytosol from the SR
How does Ca2+ binding to troponin on the thin filaments trigger the formation of cross-bridges between myosin heads and actin?
Cytosolic calcium present- binds to troponin, causing movement of troponin which in turn causes movement of tropomyosin exposing binding sites for myosin on actin. (Unblocks binding sites, cross bridges form between actin-myosin, cross bridge cycles occur, muscle cell contracts)
Describe the steps in cross-bridge cycling.
With appropriate signal the myosin heads of thick filaments attach to thin filaments (form cross-bridges) myosin heads rotate, pull thin filaments along thick filaments toward center of the sarcomere (power stroke) heads then release from active and "re-cock" can form second attachment restarting the cycle
a. How is Ca2+ removed from the cytosol in skeletal muscle cells?
Ca2+ ATPase (Ca2+ pump) in SR, transports calcium from the cytosol back into the sarcoplasmic reticulum
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