week 4 (homeostasis, endocrine/nervous system) Flashcards
homeostasis
maintaining conditions at a certian level in the body
feedback system
consist of a: stimulus (message) receptor (recievier) control centre (processes info from reiever) effector (musucle, gland, ect) reponse(alters the condition)
negative feedback
the response reduces the stimulus
reverses a change in a controlled condition
positive feedback
reinforces a change in a controlled condition
what is the difference between positive and negative feedback loops
A negative feedback system reverses
a change in a controlled condition while Unlike a negative feedback system, a
positive feedback system tends to strengthen or reinforce a change
in one of the body’s controlled conditions
how do the nervous and endocrine feedback adjustment mechanisims help with body homeostasis
it helps the body with homeostasis because it uses hormones to control thigns like blood calclium levels
feedback loops also help with reguling reflexes
components of negitive feedback loops
stimulus, sensor, control centre, effectors, response
stimulus
the change in the internal environment (movement away from the set point)
eg. body temp rising
sensor
the cells/tissue or organ which detects the stimulus and initiates a signal which will need to go to the control centre
eg. temoreceptor area of the hypothalamus or skin thermoreceptors will intitae an impulse which travels on sensory neaurons to the control centre
control centre
cell/tissue or organ which recieves signal which will need to go to the control centre
a second area of the hypothalamus called the heat losing center which initiates impulses on motor neurons to the effectors
effectors
cells/tissue or organs that recieve the signal from the contorl centre. this alters the activity of the effector. the chsnge in effector activity causes the system ti move back to the set point
eg. sweat glands release sweat on skin surface evaporation causes cooling
eg. skin capillaries dilate, increasing blood flow close to body surface. increase loss of heat
response
the result of the negitive feedback mechanism. theis result will always be the opposite to the original stimulus, causeing movement back to the setpoint
eg. the body temp is falling back to the set point
endocrine system
acts to help coordinate cell activity in tissues/organs
involves actions of hormones
hormones are transported via the blood to target glands and tissues
individual hormones are very specific in their action and can profoundly alter physiological activity of their targets
hormones
chemicals synthesized and released by endocrine glands and hormone secreting cells
what is the relationship between the nervous and endocrine system
work together to cooridinate the activity levles of the tissues/organs in the body
each system responds to specific changes in internal environment
nervous system is quick and initiates nerves impulses to alter tissue or organ activity
endocrine system responses slower and iniate a more sustained change in its target tissue
endocrine gland
The secretions of endocrine glands called hormones, enter the interstitial
fluid and then diffuse into the bloodstream without flowing through
a duct
endocrine cells
characterized by the secretion of various hormones (signaling molecules) to the blood.They produce hormones in response to nervous stimuli (changes in membrane potential). Examples are intestinal endocrine cells, cells in the adrenal medulla and pancreatic endocrine cells
circulating hormones
Most endocrine hormones are circulating hormones—they pass
from the secretory cells that make them into interstitial fluid and
then into the blood
What is the target cell of a hormone
h look at 5
what is the difference between exocrine and endocrine glands
The secretions of endocrine glands called hormones, enter the interstitial
fluid and then diffuse into the bloodstream without flowing through
a duct
secrete their products into ducts that carry the
secretions into body cavities, into the lumen of an organ, or to the
outer surface of the body. Exocrine glands include sudoriferous
(sweat), sebaceous (oil), mucous, and digestive glands
pituitary gland
by the thalamus in the brain
secretes alot lol
thyroid gland
on the trachea/larynx
secretes T3, T4 and Calcitonin
parathyriod gland
on posterior side fo thyriod
parathyriod hormone (PTH)
pancreas
pancrease in the admonen
scretes insulin and glucagon
adrenal cortex
on kidneys
secretes glucocrticoids (mainly cortisol) mineralocorticoids (mainily aldosterone) androgens(small amounts)
adrenal medulla
on kidneys
epinephrine (adenaline)
norepinephrine (noradrenaline)
ovaries
in womans reproduction system
secretes estrogen and progesterone
testes
in males reproductive system
secretes teststerone
thymus
thymus is farer down your espoguous from your thyroid
secretes thymosin
relationship between the hypothalamus and the pituitray gland
hypothalamus produces serveral hormones and two types of important connections to the pitiuotary
- hypothalamus produces horomones which are carried (by blood vessels) directly to the anterior pituitary (adenohypophysis) where they simulate or inhibit secretion of anterior pituitary hormones
- axons of neurosecretory cells extend from the hypothalalmus into the posterior pituitary (neaurohypohysis) where as a result of action potentials, they realease the hormones of the posterior pituitary
Growth Hormones (GH) or Somatotrophic Hormone (STH)
name of releasing and or inhibiting factors released by the hypothalamus:
GHRH and inhibited by PIH
the means by which these chemical factors reach the anterior pituitary:
the target gland/tissue that each hormone acts on:
liver, bone, muscules
the specific hormone action on the target gland/tissue:
induces targets to produce insulin-like gorwth factors (IGF). IGF stimulate body growth and higher metabolic rate
Thyriods-Simulating Hormone (TSH)
name of releasing and or inhibiting factors released by the hypothalamus:
TRH
the means by which these chemical factors reach the anterior pituitary:
the target gland/tissue that each hormone acts on:
Thyroid Gland
the specific hormone action on the target gland/tissue:
Simulates the release of thyroid hormone (TH). TH regulates metabolism
adrenocrtiocotropic hormone (ACTH
name of releasing and or inhibiting factors released by the hypothalamus:
CRH
the means by which these chemical factors reach the anterior pituitary:
the target gland/tissue that each hormone acts on:
Adrenal Glands
the specific hormone action on the target gland/tissue:
induces targets to produce glucocorticoids, which regulate metabolism and the stress response
follicle-stimulating hormone (FSH)
name of releasing and or inhibiting factors released by the hypothalamus:
GnRH
the means by which these chemical factors reach the anterior pituitary:
the target gland/tissue that each hormone acts on:
reproductive system
the specific hormone action on the
target gland/tissue:
stimulates production of sperm and eggs
Luteinizing hormone (LH) (interstitial cell stimulating hormone - ICSH)
name of releasing and or inhibiting factors released by the hypothalamus:
GnRH
the means by which these chemical factors reach the anterior pituitary:
the target gland/tissue that each hormone acts on:
reproductive system
the specific hormone action on the target gland/tissue:
stimulates producttion of sec hormones by gonands
oxytocin
site of syntheis and release :
the means by which these hormones reach the posterior pituitary:
control centre for their release:
Neurosecretory cells of hypothalamus secrete OT in
response to uterine distension and stimulation of
nipples.
the specific hormone action on the target gland/tissue:
Stimulates contraction of smooth muscle cells of
uterus during childbirth; stimulates contraction of
myoepithelial cells in mammary glands to cause
milk ejection.
antidiuretic hormone
site of syntheis and release :
the means by which these hormones reach the posterior pituitary:
control centre for their release:
Neurosecretory cells of hypothalamus secrete ADH
in response to elevated blood osmotic pressure,
dehydration, loss of blood volume, pain, or stress;
inhibitors of ADH secretion include low blood
osmotic pressure, high blood volume, and alcohol.
the specific hormone action on the target gland/tissue:
Conserves body water by decreasing urine volume;
decreases water loss through perspiration; raises
blood pressure by constricting arterioles.
How thyroid effects basal metabolic rate
Secretion is increased by thyrotropin-releasing
hormone (TRH), which stimulates release of
thyroid-stimulating hormone (TSH) in response
to low thyroid hormone levels, low metabolic
rate, cold, pregnancy, and high altitudes; TRH
and TSH secretions are inhibited in response to
high thyroid hormone levels; high iodine level
suppresses T3/T4 secretion.
increaases basal metabolic rate
How thyroid effects tissue growth and development
Thyroid hormones are necessary for the development of the nervous system: They promote synapse formation, myelin production,
and growth of dendrites. Thyroid hormones are also required for
growth of the skeletal system: They promote formation of ossification centers in developing bones, synthesis of many bone proteins,
and secretion of growth hormone (GH) and insulin-like growth
factors (IGFs).
How thyroid effects the nervous system
Thyroid hormones are necessary for the development of the nervous system: They promote synapse formation, myelin production,
and growth of dendrites. Thyroid hormones are also required for
growth of the skeletal system: They promote formation of ossification centers in developing bones, synthesis of many bone proteins,
and secretion of growth hormone (GH) and insulin-like growth
factors (IGFs).
how do thyroid gland and parathyroid gland work together to achieve calcium homeostatis
A higher-than-normal level of calcium ions (Ca2+) in the blood
stimulates parafollicular cells of the thyroid gland to release
more calcitonin.
Calcitonin inhibits the activity of osteoclasts, thereby decreasing
the blood Ca2+ level.
A lower-than-normal level of Ca2+ in the blood stimulates chief
PTH promotes resorption of bone extracellular matrix, which
releases Ca2+ into the blood and slows loss of Ca2+ in the urine,
raising the blood level of Ca
cells of the parathyroid gland to release more PTH.
function of nervous system
first sensory receprors of the nervous system sense any changes within the body or in the outside enironment. these receptors initiate a nerve impulse in response to this change
second integrating centres of the nervous system reieve the impulse, interpet the changes and initiate a response.
third, the response involves the transfer of a nerve impulse to a musscle or gland called the eggecyor to change its activity
central nervous system
consists of the brain and spinal cord
peripheral nervous system
contains sensory neurons
motor neurons
motorneurons contain:
somaitc NS and autonomic NS
autonomic NS contains:
parasympathic divison and sympathic divison
brain
reieves and processes sensory information, intiates responses, stores memories, generates thoughts and emotions
spinal cord
conducts signals yo and from the brain, controls relex activites
motor neurons
CNS to musucles and glands
efferent (away from CNS)
sensory neurons
sensory organs to CNS
afferent (towards CNS)
somatic NS
controls voluntary movemements
autosomic NS
controls involuntary reponses
sympathic diviison
fight or flight
parasympathic divison
rest or digest
enteric nervous system
an extensive network of over 100 million
neurons confined to the wall of the gastrointestinal (GI) tract. The ENS
helps regulate the activity of the smooth muscle and glands of the GI
tract. Although the ENS can function independently, it communicates
with and is regulated by the other branches of the ANS
neuron
nerve cells
possess electrical excitability the ability to respond to a stimulus and convert it into an action potential
neurons also connect all
regions of the body to the brain and spinal cord. As highly specialized
cells capable of reaching great lengths and making extremely intricate connections with other cells, neurons provide most of the
unique functions of the nervous system, such as sensing, thinking,
remembering, controlling muscle activity, and regulating glandular
secretions.
neroglia
support, nourish, and protect neurons, and maintain the interstitial fluid that bathes them
are smaller cells,
but they greatly outnumber neurons
cell body*
contains a nucleus
surrounded by cytoplasm that includes typical cellular organelles
such as lysosomes, mitochondria, and a Golgi complex.
nerve fibres*
r is a general term for any neuronal process (extension) that emerges from the cell body of a neuron. Most neurons have
two kinds of processes: multiple dendrites and a single axon
denrite*
are the receiving or input portions of a
neuron. The plasma membranes of dendrites (and cell bodies) contain numerous receptor sites for binding chemical messengers from
other cells.
Dendrites usually are short, tapering, and highly branched.
In many neurons the dendrites form a tree-shaped array of processes
extending from the cell body.
Their cytoplasm contains Nissl bodies,
mitochondria, and other organelles
axon(axon collaterals)*
propagates nerve impulses
toward another neuron, a muscle fiber, or a gland cell.
An axon is a
long, thin, cylindrical projection that of en joins to the cell body at a
cone-shaped elevation called the axon hillock
synaptic end bulb*
tips of
some axon terminals swell into bulb-shaped structures
contain many tiny membrane-enclosed sacs called synaptic vesicles
that store a chemical called a neurotransmitter
synaptic vesicle*
tiny membrane-enclosed sacs
store a chemical called a neurotransmitter
myelin sheath*
axons surrounded by a multilayered lipid
and protein covering,
The sheath electrically insulates the axon of a
neuron and increases the speed of nerve impulse conduction
schwann cell*
These cells encircle PNS axons. they form the myelin sheath around axons.each Schwann cell myelinates a single axon
neurolemma*
The outer nucleated
cytoplasmic layer of the Schwann cell, which encloses the myelin
sheath, is the neurolemma
the synapse
a region where
communication occurs between two neurons or between a neuron
and an ef ector cell (muscle cell or glandular cell).
synaptic end bulb
end bulb contains synaptic vesicles which are filled with a neurotransmitter substance. When a nerve impulse travels down the axon and reaches the end bulb the neurotransmitter is released into a small space, the synaptic cleft
synaptic cleft
a space of 20–50 nm* that is filled
with interstitial fluid
space between the synapses
neurotransmitter substances
A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a synapse. The cell receiving the signal, or target cell, may be another neuron, but could also be a gland or muscle cell
neaurotransmitter receptors
neurotransmitters released from a presynaptic neuron bind to neurotransmitter receptors in the plasma
membrane of a postsynaptic cell
synaptic vesicles
synaptic vesicles (or neurotransmitter vesicles) store various neurotransmitters that are released at the synapse
pre synaptic cells
refers to a nerve cell that carries a nerve
impulse toward a synapse. It is the cell that sends a signal.
post synaptic cells
is the cell that receives a signal.
PNS main neurotransmitters
acetylcholine
axons which release acethlcholine as their neurotransmitter are called cholinegric fibers
norepinephrine (noradrenlin)
axons which release norepinephrine as their neurotransmitter are called adrenergic fibres
CNS main neaurotransmitters
serotonin
dopamine
multipolar neuron*
usually have several dendrites and one axon
Most neurons in the brain and spinal cord are of this
type, as well as all motor neuron
bipolar neuron*
have one main dendrite and one axon
They are found in the retina of the eye, the inner ear,
and the olfactory area of the brain
unipolar neauron*
have dendrites and one axon that are fused
together to form a continuous process that emerges from the cell
body
sensory neurons* (afferent)
Once an appropriate
stimulus activates a sensory receptor, the sensory neuron forms an
action potential in its axon and the action potential is conveyed
into the CNS through cranial or spinal nerves. Most sensory neurons are unipolar in structure.
motor neurons* (efferent)
convey action potentials away from the CNS to effectors (muscles
and glands) in the periphery (PNS) through cranial or spinal nerves
Motor neurons are multipolar in structure.
interneuron*
mainly located within the
CNS between sensory and motor neurons
Interneurons integrate (process) incoming sensory information
from sensory neurons and then elicit a motor response by activating the appropriate motor neurons. Most interneurons are multipolar
in structure.
how are nerve impulses produced and transmitted along neurons
nerve impulses are produced and transmitted along sxons by means of the movement of ions, specifically sodium (Na+) and potassium (K+) across neuron membrane
resting state
The resting membrane potential of a neuron is about -70 mV (mV=millivolt) - this means that the inside of the neuron is 70 mV less than the outside. At rest, there are relatively more sodium ions outside the neuron and more potassium ions inside that neuron
thershold
level of stimulsis needed to cause action poential, all or nothing response, -65mV
depolarization (rising phase)
When the response makes the membrane
less polarized (inside less negative), it is termed a depolarizing
graded potential
closer to action potential
the negative membrane
potential becomes less negative, reaches zero, and then becomes
positive
repolarization (fallling phase)
the membrane potential is
restored to the resting state of − 70 mV
hyperpolarization (undershoot phase)
When the
response makes the membrane more polarized (inside more negative), it is termed a hyperpolarizing graded potential
farher away from action potential
sensory receptor*
The distal end of a sensory neuron (dendrite)
or an associated sensory structure serves as a sensory receptor.
It responds to a specific stimulus—a change in the internal or
external environment—by producing a graded potential called a
generator (or receptor) potential
effector *
The part of the body that responds to the motor nerve
impulse, such as a muscle or gland, is the ef ector. Its action is
called a reflex. If the ef ector is skeletal muscle, the reflex is a
somatic reflex. If the ef ector is smooth muscle, cardiac muscle,
or a gland, the reflex is an autonomic (visceral) reflex
gray matter of the spinal cord*
inside of spinal cord
The gray matter
of the spinal cord is shaped like the letter H or a butterfly; it consists of
dendrites and cell bodies of neurons, unmyelinated axons, and neuroglia
. The spinal cord gray matter is a site for integration (summing) of excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs)
white matter of the spinal cord*
outside of spinal cord
The white
matter of the spinal cord consists primarily of bundles of myelinated
axons of neurons.
The white matter of the spinal cord contains sensory and motor tracts, the
“highways” for conduction of sensory nerve impulses toward the brain and
motor nerve impulses from the brain toward ef ector tissues
tract (sensory and motor) of the spinal cord*
Sensory input is conveyed from sensory receptors to the posterior gray horns of the spinal cord, and
motor output is conveyed from the anterior and lateral gray horns of the spinal cord to ef ectors
(muscles and glands)
nerves (sensory, motor and mixed)*
sensory:The nerve impulses propagate from the sensory receptor along the axon of the sensory neuron to the
axon terminals, which are located in the gray matter of the spinal
cord or brainstem. From here, relay neurons send nerve impulses
to the area of the brain that allows conscious awareness that the
reflex has occurred
motor: Impulses triggered by the integrating centernpropagate out of the CNS along a motor neuron to the part of the
body that will respond
mixed:Mixed nerves are composed of both motor and sensory fibers, and transmit messages in both directions at once
ganglia of PNS*
Ganglia are always in the PNS, usually very closely associated with CNC
Spinal or cranial nerves
They are just bundles of neuron cell bodies
nuclei of CNS*
They are just bundles of neuron cell bodies
reflex arc*
The pathway followed by nerve impulses that produce a reflex is a reflex arc.
contains 5 fundamental functions sesnroy receptor sesnroy neauron integrating centre motor neuron effector
exteroceptors
are located at or near the
external surface of the body; they are sensitive to stimuli originating outside the body and provide information about the external
environment. The sensations of hearing, vision, smell, taste,
touch, pressure, vibration, temperature, and pain are conveyed by
exteroceptors
visceroceptors
are located in
blood vessels, visceral organs, muscles, and the nervous system and
monitor conditions in the internal environment. The nerve impulses
produced by interoceptors usually are not consciously perceived;
occasionally, however, activation of interoceptors by strong stimuli
may be felt as pain or pressure
proprioceptors
are located in muscles, tendons, joints, and the inner ear. They provide information about body
position, muscle length and tension, and the position and movement of your joints.
describe the pathway that a nerve impulse follows from sensory receptor in the neuron relax arc to effector*
sensroy receptor to sensroy neuron to integrating centre to motor neuron to effector
general functions of the brain
the brain is the centre for resigtering sensations, correlating them with one another and with stored information, making decisionis and initing muscle or glandylar responses. it contains control centres for visceral activity and is the control centre for cranial reflexes. it is also the centre for intellect, emotions, behaviour and memory
two functions of the spinal cord
the spinal cord functions as a two way conduction pathway between the brain and spinal nerves
the spinal cord is the control centre for the spinal reflexes
difference between spinal and cranial nerves
Cranial nerves are those that emerge directly from the brain. Spinal nerves are those that emerge directly from segments of the spinal cord. Cranial nerve transfers information between the brain and the other parts of the body
hormone
is a molecule that
is released in one part of the body but regulates the activity of cells in
other parts of the body
local hormone
act locally on neighboring cells or on the same cell that
secreted them without entering the bloodstream
intergrating centre
One or more regions of gray matter within the
CNS acts as an integrating center. In the simplest type of reflex, the
integrating center is a single synapse between a sensory neuron
and a motor neuron
Cerebrum
Literally “the understanding”
• Virtually all higher cognitive functions
• Reading, writing, speaking, math, science, music, memory, imagination
• Main components
• Outer cerebral cortex
• Inner cerebral white matter
• Gray matter nuclei within white matter
Humoral Stimuli
Changing blood levels of ions and
nutrients directly stimulate secretion
of hormones
Hormonal Stimuli
Hormones stimulate other endocrine
organs to release their hormones
Hypothalamic hormones stimulate
release of most anterior pituitary
hormones
Anterior pituitary hormones
stimulate targets to secrete still
more hormones
Hypothalamic-pituitary-target endocrine organ feedback loop: hormones from final target organs inhibit release of anterior pituitary hormones
Neural Stimuli
Nerve fibers stimulate hormone
release
Hypothalamic Control
Control may be direct or indirect
(through the reticular system)
Centers of the hypothalamus control – Heart activity and blood pressure – Body temperature, water balance,
and endocrine activity – Emotional stages (rage, pleasure)
and biological drives (hunger, thirst,
sex) – Reactions to fear and the “fight-orflight” system
Permissiveness
one hormone cannot exert its effects without another
hormone being present
Synergism
more than one hormone produces same effects on target cell
amplification
Antagonism:
one or more hormones oppose(s) action of another hormone
two lobes of pituitary gland
Posterior pituitary (lobe) • Neural tissue
Anterior pituitary (lobe) (adenohypophysis) • Glandular tissue
posterior pituitary
Posterior pituitary (lobe) Downgrowth of hypothalamic neural tissue
Neural connection to hypothalamus (hypothalamic-hypophyseal tract)
Nuclei of hypothalamus synthesize neurohormones oxytocin and antidiuretic hormone (ADH)
Neurohormones are transported to and stored in posterior pituitary
anterior lobe
Originates as out-pocketing of oral mucosa
Vascular connection to hypothalamus Hypophyseal portal system Primary capillary plexus Hypophyseal portal veins Secondary capillary plexus
Carries releasing and inhibiting
hormones to anterior pituitary to
regulate hormone secretio
