ANFS345

Exam #2

what is a reflex action?

a fast, involuntary response to a stimulus; requires a stimulus and a response (involuntary)

how do reflex actions work?

if there’s stress on/in the body, the body will sense it, and send info through the afferent and efferent systems, back to the muscles to respond to the stimulus

how does muscle movement work?

when one muscle flexes, the other contracts in response; 1 muscle is never working on it’s own to perform a task

what are muscles made out of?

muscle fibers

what are the types of muscle fibers?

extrafusal and intrafusal

what do extrafusal muscles do?

heavy lifting 

what do intrafusal muscles do?

fine motor control

what neurons are responsible for telling muscle fibers what to do?

alpha motor, gamma motor, and group 1 afferent axons

what do alpha motor neurons do?

tells extrafusal muscles what to do (contract); when a muscle contracts, another muscle flexes in response

what do gamma motor neurons do?

feeds the intrafusal muscle fibers

what do group 1 afferent axons do?

bring info from the intrafusal muscles to the CNS for processing 

what is the ‘normal state’ of motion of a muscle?

perpetual stretch; there are signals constantly being sent from afferent neurons to the CNS whether anything is happening that requires ‘work’

how does flight occur?

depressor and levator muscles

what do depressor muscles do in flight?

contract/depress the wing; the depression of the wing is sensed by receptors that the depression is occurring, which activates the levator muscle 

what do levator muscles do in flight?

changes the position of the wings up and down (elevates)

what is central control hypothesis?

environment based theory that describes how muscles work;  no receptors in this hypothesis, the muscle instead knows when to function because of an internal clock/generator that periodically activates, which leads to a central pattern generator

what is a central pattern generator?

it is a neural circuit that generates rhythmic behaviors. (Rhythmic activities, such as walking, are generated in the spinal cord)

when is the central pattern generator activated in flight?

when there is wind; deactivated when there is an absence of leg control with the ground

what does the central pattern generator do?

sends signals to the levator muscle, then depressor, over and over to create movement

what is oscillation?

the back and forth movement of air molecules because of a vibrating object

what are the types of oscillation patterns associated with the central pattern generator?

back and forth oscillation with impulses, oscillation without impulses, a closed loop oscillation, a half-center model

what is the premotor region of the brain?

the region of the brain that allows for locomotion in high vertebrates

what is the primary motor cortex?

a part of the premotor region of the brain that activates pyramidal cells and aid in the locomotion of limbs

what are pyramidal cells in the brain?

cells that activate spinal motor circuits via the brainstem and motor nuclei in order to create change in motion? (flexor activity)

what connects bundles of muscle fibers?

connective tissue

what structures make up muscle fiber cells?

nucleus, mitochondria, sarcolemma, sarcoplasmic reticulum, t-tubule, myofibrils, terminal cisternae

what is the sarcolemma?

muscle cell membrane that covers the entire muscle fiber cell

what is the sarcoplasmic reticulum?

the sarcoplasmic reticulum is a modified endoplasmic reticulum that stores calcium ions (in a muscle cells) that spans between the myofibrils

what is a myofibril?

ribbon-like organelle of the muscle fiber cells

bundles of myofilaments

made up of sarcomeres and other structures

what is a sarcomere?

functional unit of the muscle

what structures made up of sarcomeres?

I-Bands, A-Bands, H zones, Z disc, and M line

what makes up a sarcomere?

actin and myosin

what is actin?

thin filament protein

what is myosin?

thick filament protein with a head and tail end 

what can you find on the head of myosin?

ATP and actin binding sites

what will you find attached to actin?

troponin and tropomyosin

what happens to sarcomeres when a muscle contracts?

the thin and thick filaments (actin and myosin) are linked closer together, the H zone shrinks, the myosin moves towards the M line, the I-Band shrinks, the Z disc moves closer to the M line

will a muscle always perform the action it’s contracting for?

no; a muscle can contract but not carry out a function. you can even have action be carried out without any change in muscle length (shrinkage or stretch)

what is isometric contraction?

the elastic sides of sarcomeres ends stretch (not the sarcomeres itself), but there’s no change in length of the muscle; there isn’t enough tension to do ‘work’

what is isotonic concentric contraction?

muscle contracts, and maintains constant tension while the muscle shortens

what is isotonic eccentric contraction?

when the muscle extends and stretches

what is rigor?

lack of movement due to ATP; a dead body doesn’t have any ATP

what is ATP?

energy used for contraction of muscles, among other things

what happens when all ATP is used up?

our bodies will use a stored form of ATP called creatine phosphate, which the body will break down into creatine, which then releases the ATP

what other processes generate ATP?

glycolysis

what is glycolosis?

the breakdown of glucose, gives instant ATP

anaerobic

produces lactic acid, which is used for energy

what does lactic acid do for the body?

increases pH, which is why your muscles hurt when you run for the first time in a while

what is the endocrine system?

system that creates, regulates, and controls hormones

what controls/influences the endocrine system?

the nervous system

what are the cells responsible for sending chemical signals?

neurons, non-neural endocrine cells, neurosecretory cells, local paracrine and autocrine cells 

what happens with a neural chemical signal?

presynaptic neuron sends signal to postsynaptic neuron; only sends to that one cell (the postsynaptic neuron or muscle if it’s at neuromuscular junction), covers a small distance 

what happens with a non-neural endocrine chemical signal?

a cell is capable of producing a hormone, and it’s released into the blood; only affects cells that have receptors for that hormone

what happens with paracrine and autocrine chemical signals?

the signals get sent into the generate vicinity of the releasing cell, and cells around it pick it up; relates to the amplification of the signal

what are neurons?

neurotransmitters

what are gap junctions?

small tunnels in cells cytoplasm that open up to other cells so that the cells make cytoplasmic contact

what are steroids?

derived from lipids

where do steroids come from?

cholesterol

what are some examples of steroids?

aldosterone, cortisol, testosterone, estradiol 

what are amine hormones?

hormones derived from amino acids 

what are the most common amino acids we get amine hormones from?

tyrosine and tryptophan

what are the types of amine hormones?

dopamine, norepinephrine, epinephrine, triiodothyronine, thyroxine, melatonin

what are peptide/protein hormones?

hormones that require a lot of amino acids that form peptides to form

what are some common peptide/protein hormones?

insulin and GnRH

what is insulin?

a hormone which converts glucose into glycogen (controls blood sugar)

what is GnRH?

gonadotropin releasing hormone (sex hormone 

how is insulin made in the body?

The ribosome from the rough endoplasmic reticulum takes mRNA to make preprohormone proteins. Preprohormone’s first segment (P segment) is chopped off and separated, which converts the preprohormone into proinsulin, and moves to the Golgi apparatus vesicles. The middle portion (C region) is chopped off, and the pre- and post- sections of the proinsulin link together by using disulfide bonds to form mature insulin (C is repurposed to create more proinsulin later).

what parts of the brain control the endocrine system?

hypothalamus and posterior pituitary

what part of the brain controls the posterior pituitary?

hypothalamus

what does the hypothalamus do?

creates hormones that are sent to posterior and anterior pituitary and when it thinks there is need for those hormones, it signals to the posterior pituitary to release the hormones

what does the posterior pituitary?

stores hormones produced by the hypothalamus?

what hormones does the hypothalamus make/posterior pituitary release?

vasopressin (AKA ADH/AVP)

what is the anterior pituitary?

an important endocrine organ that produces hormones

what hormones are produced by the anterior pituitary?

thyrotropin, adrenocorticotropin (ACTH), growth hormone, gonadotropins, prolactin, MSH 

what is the adrenal gland?

an organ that sits on top of the kidneys

what are the layers of the adrenal glands?

medulla, zona reticularis, zone fasciculata, zona glomerulosa

what is the function of the medulla of the adrenal gland?

secretes catecholamines

what is the function of the zona reticularis of the adrenal gland?

produces androgens (sex hormones)

what is the function of the zona fasciculata of the adrenal gland?

produces glucocorticoids

what is the function of the zona glomerulosa of the adrenal gland?

produces mineralocorticoids

what is the HPA axis?

the hypothalamus-pituitary-adrenal axis

what is the function of the HPA axis?

senses and responds to stress (fight of flight)

what happens when an animal has stress (within the endocrine system)?

it leads to the activation of the sympathetic system (fight or flight) and more secretion of CRH from the hypothalamus 

what does CRH do?

tells the anterior pituitary to produce ACTH?

what is CRH?

corticotropin releasing hormone

what is ACTH?

adrenocorticotropin hormone

what is ACTH do?

stimulates adrenal cortex to release cortisol 

what else besides the hypothalamus can ACTH be produced?

immune cells

what hormones does the sympathetic system release?

norepinephrine and epinephrine

what does norepinephrine do?

helps control alertness and arousal

what does epinephrine do?

increase heart rate, fight or flight, focus

what does the release of norepinephrine and epinephrine signal/stimulate?

the amygdala and hippocampus; tells them whether to remember the events 

what are the early psychological effects of stress in mammals?

Increase in heart rate, higher ventilation (breathing), and greater degree of vasoconstriction (blood pressure increase to increase O2 in muscles), lowers digestion, increases glucagon production, increases fat breakdown, decreases insulin levels, increase glucose release

what do the release of vasopressin and CRH lead to in the mammalian stress response?

leads to ACTH production, which leads to glucocorticoid production 

what are some delayed physiological effects of the mammalian stress response?

related to the release of glucocorticoids: oppose the actions of insulin, breakdown energy instead of storing, increases gluconeogenesis, increase of amino acids, increase breakdown of muscle and bone, fat breakdown (catabolism), leads to fatty acids, inhibits TSH, gonadotropins, and GH

what else besides ACTH production can your immune cells do in the endocrine system?

signal to the adrenal glands (independent of CRH), release cytokines

what are cytokines?

chemical messengers that stimulate the brain to release CRH, which creates glucocorticoids

what is insulin?

a hormone secreted in response to carbs

what stimulates the release of insulin the body?

when your body has a high level of carbs

what does insulin do?

allows for the breakdown of carbs into glucose and other compounds 

what is glucagon?

a hormone secreted when blood glucose is low (when you need carbs/when theres an absence of carbs)