Chapter 12 Flashcards
2 important functions of the human digestive system
- breaking down large food molecules into smaller, usable molecules
- absorbing these smaller molecules
What is each one broken down into? fats starch nucleic acids proteins
glycerol and fatty acids
monosaccharides
nucleotides
amino acids
Vitamins and mineral are small enough to
be absorbed without being digested
3 main characteristics of the digestive tract
- 30 feet long
- made of smooth (involuntary) muscle that pushes food along by a process called peristalsis
- muscles of the tract are controlled by the autonomic nervous system
What begins at the mouth?
mechanical/chemical digestion
What enzyme begins starch digestion? Where is this enzyme?
salivary amylase in saliva
What breaks down food mechanically?
tongue and differently shaped teeth work together
The type of teeth an animal has is a:
Humans are omnivores and have 3 different types of teeth:
reflection of its dietary habits
incisors for cutting, canines for tearing, molars for grinding
What digestion occurs in the esophagus?
none
Food in the esophagus is
directed away from the windpipe by the epiglottis ( a flap of cartilage in the back of the pharynx, throat)
Esophagus transports food from
throat to stomach
Both _____ and ______ digestion occur in the stomach
mechanical and chemical
What begins in the stomach?
protein digestion
What do the stomach’s thick/muscular walls do?
churn food mechanically + secrete gastric juice which contains hydrochloric acid and enzymes that digest proteins
Hydrochloric acid
- begins the breakdown of muscle (meat)
- activates the inactive enzyme pepsinogen to become pepsin, which digests protein
Enzyme ‘rennin’
aids in the digestion of the protein in milk
pH of the stomach
2-3
What does the cardiac sphincter do? Where is it?
located at the top of the stomach
keeps acidified food in the stomach from backing up into the esophagus and burning it
What is the pyloric sphincter?
Where is it?
the bottom of the stomach
keeps food in the stomach long enough to be digested
What can excessive acid in the stomach do?
can cause an ulcer to form in the esophagus, the stomach, or the duodenum ( the upper intestine)
Common cause of ulcers and treatment
bacterium, heliobacter pylori
antibiotics
Small intestine
-all digestion is completed and nutrients are absrobed here
2 characteristics of small intestine
- ph is 8
- 6 meters long
All digestion is completed in the
duodenum, the first 10 inches of the small intestine
The intestinal enzymes are
amylases, proteases, lipases, and nucleases
Pancreatic amylases
digest starch
secreted into the small intestine
Peptidases
- ex. trypsin and chymotrypsin
- continue to break down proteins
Nucleases
hydrolyze nucleic acids into nucleotides
Lipases
break down fats
What lines the small intestine?
villi, millions of them, ‘fingerlike’
-absorb all nutrients that were previously released from digested food
Each villus contains
capillaries, which absorb amino acids, vitamins, and monosaccharides directly into the bloodstream
Each villus also contains a
lacteal, which absorbs fatty acids and glycerol into the lymphatic syste,
Villi have microscopic appendages called
microvilli that further enhance the rate of absorption
liver
produces bile that converts fats
Bile
pH = 11 neutralizes chyme (acidified food from stomach) entering small intestine
Other functions of the liver include
- breaks down food/recycle RBCs
- detoxifies blood-removes alcohol and drugs
- produces cholesterol necessary for structure of cell membranes
- produces the nitrogenous waste urea from protein metabolism
Remember
Bile is not
an enzyme
Gallbladder
- stores bile that is produced in liver
- bile emulsifies fats in small intestine
- body can function well without a gallbladder
2 functions of the pancreas
- produces enzymes that break down carbs (amylases), proteins (peptidases), lipids (lipases), and nucleic acids, and secretes them into the small intestine
- produce sodium bicarbonate
Sodium Bicarbonate
a base that neutralizes stomach acid, enabling intestinal enzymes, which require a basic environment, to be effective
Since the pancreas is part of the endocrine system,
it produces hormones to control blood sugar levels
Large intestine or colon
no digestion occurs here
3 major functions of large intestine or colon
egestion
vitamin production
reabsorption of water
Egestion
removal of undigested waste
Vitamin production
bacteria symbionts living in the colons produce the B vitamins, folic acid, and vitamin K
Reabsorption of water
constipation- too much water is reabsorbed from the intestine into body
diarrhea- an inadequate amount of water is absorbed back into body
Reabsorption of water
constipation- too much water is reabsorbed from the intestine into body
diarrhea- an inadequate amount of water is absorbed back into body
Rectum
egestion- removal of undigested waste
last 7-8 inches of the gastrointestinal tract stores feces until their release through the anus
Rectum
egestion- removal of undigested waste
last 7-8 inches of the gastrointestinal tract stores feces until their release through the anus
Air enters the nasal cavity and is
moistened, warmed, and filtered
Second, air passes through the larynx and
down the trachea and bronchi into the tiniest bronchioles, which end in microscopically tiny air sacs called alveoli
Why do humans have an internal respiratory surface?
because respiratory gases are exchanged deep inside the body
The rib cage _______ and forces the _______ to contract and move ________, thus expanding the ____ _______ and decreasing the _______ _________.
expands diaphragm downward chest cavity internal pressure
Why is air drawn into the lungs by negative pressure?
because the internal pressure inside the chest cavity is lower than the air pressure surrounding the body
What is the medulla’s (brain) role in respiration?
sets the breathing rhythym by monitoring CO2 levels in blood and by sensing changes in the pH of the blood
Blood pH lower than 7.4 triggers
autonomic nerves from the medulla to increase the breathing rate to rid the body of more CO2
The concentration of oxygen in the blood usually has
little effect on the breathing control centers
What is oxygen in the blood carried by? What does it combine with?
by respiratory pigment hemoglobin
combines loosely with oxygen molecules to form molecule oxyhemoglobin
CO2 is the
by-product of cell respiration
CO2 is released from
every cell and dissolves in the blood
CO2 is carried in the plasma as part of the
reversible blood-buffering carbonic acid-bicarbonate ion system
carbonic acid-bicarbonate ion system
maintains blood at a constant pH
human circulation consists of a
closed circulatory system with arteries, veins, and capillaries
Vessel: Artery
Function:
Structure:
carries blood away from the heart under enormous pressure
walls are made of thick layer of elastic, smooth muscle and can withstand high pressure/contract and expand as needed
Vessel: Vein
Function:
Structure:
carries blood back to the heart under very little pressure
-walls don’t contain thick layer of muscle, has valve to help prevent backflow, located within skeletal muscle which propels blood upward and back to heart as the body moves and muscles contract
Vessel: Vein
Function:
Structure:
carries blood back to the heart under very little pressure
-walls don’t contain thick layer of muscle, has valve to help prevent backflow, located within skeletal muscle which propels blood upward and back to heart as the body moves and muscles contract
Vessel: Capillary
Function:
Structure:
allows for diffusion of nutrients and wastes between cells and blood
-blood travels slowly here to allow time for diffusion of nutrients and wastes
Blood consists of
several different cell types suspended in a liquid matrix called plasma
How much blood does the average human body contain?
4-6 liters of blood
Blood clotting
a complex mechanism that begins with the release of clotting factors from platelets and damaged tissue
Anticlotting factors
constantly circulate in the plasma to prevent the formation of a clot or thrombus, which can cause serious damage in the absence of injury
Serum is
plasma minus clotting factors
What’s necessary for normal blood clotting?
calcium
Component: plasma
Scientific name:
Properties:
none
liquid portion of the blood
contains clotting factors, hormones, antibodies, dissolved gases, nutrients, and wastes
90% water
Component: RBCs
Scientific name:
Properties:
erythrocytes carry hemoglobin and oxygen don't have a nucleus live about 120 days formed in the bone marrow and recycled in the liver
Component: White blood cells
Scientific name:
Properties:
leukocytes
fight infection
formed in the bone marrow
die fighting infection and are 1 component of pus
Component: Platelets
Scientific name:
Properties:
thrombocytes
clot blood
cell fragments that are formed in the bone marrow from megakaryocytes
Heart location and size
Beats about
beneath the sternum
size of clenched fist
70 beats per minute and pumps about 5 liters of blood
2 atria
receive blood from the cells of the body and 2 ventricles pump blood out of the heart
SA
sinoatrial node
sets the timing of the contractions of the heart
Electrical impulses travel through the
cardiace and body tissues to the skin
What is the heart’s pacemaker influenced by?
nervous system
hormones such as adrenaline and body temperature
Blood pressure is lowest in the
veins and highest in the arteries when the ventricle contract
Systolic number (120)
is a measurement of the pressure when the ventricle contract
Diastolic (80)
a measure of the pressure when the heart relaxes
Pathway of blood
blood enter the heart through the vena cava and continues to the
- right atrium
- right atrioventricular (AV) valve or tricuspid valve
- right ventricle
- pulmonary semilunar valve
- pulmonary artery
- lungs
- pulmonary vein
- left atrium
- left atrioventricular (AV) valve or bicuspid valve
- left ventricle
- aortic semilunar valve
- aorta
- to all the cells in the body
- returns to the heart through the vena cava
Blood circulates through the
coronary circulation (heart), renal circulation (kidneys), and the hepatic circulation (liver)
Pulmonary circulation
includes pulmonary artery, lungs, and the pulmonary vein
The pulmonary artery is the only artery that carries
deoxygenated blood and the pulmonary vein is the only vein that carries oxygenated blood
What are the 2 major regulatory systems that release chemicals?
endocrine and nervous system
Endocrine system secretes
Nervous system secretes
hormones
neurotransmitters
Epinephrine functions boths as the
fight or flight hormone secreted by the adrenal gland
neurotransmitter that sends a message from one neuron to another
Hormones are produced in
ductless (endocrine) glands and move through the blood to a specific target cell , tissue, or organ that can be far from the original endocrine gland
Hormones can either be
immediate short lived responses or
dramatic long-term development of an entire organism
Tropic hormones
hormones that stimulate other glands to release hormones and can have a far-reaching effect
Example of tropic hormones
TSH- thyroid stimulating hormone
anterior pituitary region in the brain stimulates the thyroid to release thyroxin
Pheromones
in the urine of a dog carry a message between different individuals of the same species
Hypothalamus
bridge between the endocrine and nervous system
Hypothalamus as a part of the nervous system
sends electrical signals to the adrenal gland to release adrenaline
Hypothalamus as a part of the endocrine gland
produces oxytocin and antidiuretic hormone that it stores in the posterior pituitary
Hypothalamus also contains the body’s
thermostat and centers for regulating hunger and thirst
Anterior pituitary gland
examples of hormones
growth hormone GH luteinizing hormone LH thyroid-stimulating hormone TSH adrenocorticotropic hormone ACTH follicle-stimulating hormone FSH
Anterior pituitary functions
stimulates growth of bones
stimulates ovaries and testes
stimulates thyroid gland
stimulates adrenal cortex to secrete glucocorticoids
stimulates gonads to produce sperm and ova
Posterior pituitary hormones
oxytocin
antidiuretic hormone ADH
Posterior pituitary functions
stimulates contractions of uterus and mammary glands
promotes retention of water by kidneys
Thyroid Hormones
thyroxin
calcitonin
Thyroid functions
controls metabolic rate
lowers blood calcium levels
Parathyroid Hormone
parathormone
Parathyroid functions
raises blood calcium levels
Adrenal cortex hormone
glucocorticoids
Adrenal cortex function
raises blood sugar levels
Adrenal medulla hormones
epinephrine (adreline)
nonepinephrine (noradrenaline)
Adrenal medulla function
raises blood sugar level by increasing rate of glycogen breakdown by liver
Pancreas-islets of Langerhans hormones
insulin
glucagon
Pancreas- isets of Langerhans functions
lowers blood glucose levels
raises blood glucose levels
Thymus (in neck) hormone
thymosin
Thymus (in neck) function
stimulates T lymphocytes as part of the immune response
Pineal (in brain) hormone
melatonin
Pineal (in brain) function
involved in biorhythms
Ovaries hormones
estrogen
progesterone
Ovaries function
stimulates uterine lining, promotes development and maintenance of primary and secondary characteristics of females
promotes uterine lining growth
Testes Hormones
androgens
Testes functions
support sperm production and promote secondary sex characteristics
2 types of hormones
steroid
nonsteroidal or polypeptide hormones
-each stimulate target cells in different ways
Lipids or Steroid hormones
- diffuse directly through the plasma membrane
- bind to a receptor inside the cell that triggers the cell’s response
Protein or polypeptide hormones (nonsteroidal)
-cannot dissolve in the plasma membrane so they bind to a receptor on the surface of the cell
In nonsteroidal hormones, the hormone (the first messenger) binds to a
receptor on the surface of the cell, it triggers a secondary messenger such as c-AMP, which converts the extracellular chemical signal to a specific response inside the cell
Feedback mechanism
a self-regulating mechanism that increases or decreases an action or the level of a particular substance
Positive feedback
enhances an already existing response
Example of positive feedback
during childbirth, the pressure of the baby’s head against sensors near the opening of the uterus stimulates more uterine contractions which causes increased pressure against the uterine opening, which causes more contractions
-this positive feedback loop brings labor to an end and the birth of a baby
Negative feedback
a common mechanism in the endocrine system (and elsewhere) that maintains homeostasis
Example of negative feedback
when the thyroxin in the blood is too low, the hypothalamus stimulates the anterior pituitary to release a hormone, thryoid-stimulating hormone (TSH), which stimulates the thyroid to release more thyroxin
-when the level of thyroxin is adequate, the hypothalamus stops stimulating the pituitary
The vertebrate nervous system consists of
central and peripheral components
The central nervous system (CNS) consists of
the brain and spinal cord
The peripheral nervous system (PNS) consists of
all nerves outside the CNS
Peripheral nervous system is further divided into
sensory- conveys information from sensory receptors or nerve endings
motor- stimulates voluntary and involuntary muscles and consists of two more systems
Motor system is further divided into
somatic- controls voluntary muscles
autonomic- controls involuntary muscles
Sympathetic
- fight or flight response
- increases heart and breathing rate
- liver converts glycogen to glucose
- bronchi of lungs dilate and increase gas exchange
- adrenaline raises blood glucose levels
Parasympathetic
- opposes the sympathetic system
- calms the body
- decreases heart/breathing rate
- enhances digestion
Neuron
basic functional unit of the nervous system
-consists of a cell body which contains nucleus and other organelles and 2 types of cytoplasmic extensions called dendrites and axons
Dendrites
sensory
receive incoming messages from other cells and carry the electrical signal to the cell body
-neurons can having 100s of dendrites
Axons
transmit an impulse from the cell body outward to another cell
-neuron can only 1 axon which can be several feet long in large mammals
Most axons are wrapped in a
myelin sheet that protects the axon and speeds the impulse
What’s the simplest nerve response?
a reflex arc
Reflex arc is
inborn, automatic, and protective
Example of a reflex arc
knee-jerk reflex- consists of only a sensory and a motor neuron
-the impulse moves from the sensory neuron in your knee to the motor neuron that directs the thigh muscle to contract, spinal cord is not involved in this type of reflex
A more complex reflex arc consists of 3 neurons:
sensory, motor, and an interneuron or association neuron
Explain a complex reflex arc
a sensory neuron transmits an impulse to the interneuron in the spinal cord which sends 1 impulse to the brain for processing and also one to the motor neuron to effect change immediately (at the muscle)
All living cells exhibit a membrane potential
a difference in electrical charge between the cytoplasm (negative charge) and extracellular fluid (positive charge)
How do physiologists measure membrane potential?
its between -500 mV to -100 mV
-the negative sign indicates that the inside of the cell is negative relative to the outside of the cell
Resting Potential
A neuron at rest or unstimulated (resting potential)
is polarized and has a membrane potential of about -70 mV
How did the sodium-potassium pump maintain this polarization?
by actively pumping ions out of the cell that leak inward
In order for the nerve to fire, a stimulus must be
strong enough to overcome the resting threshold or resting potential
The larger the membrane potential, the
stronger the stimulus must be to cause the nerve to fire
Action potential or impulse
can only be generated in the axon of a neuron
When an axon is stimulated sufficiently to overcome the threshold,
the permeability of a region of the membrane suddenly changes
Sodium channels open and sodium
floods into the cell, down the concentration gradient
in response, potassium channels open and potassium floods out of the cell
This rapid movement of ions or wave of depolarization
reverses the polarity of the membrane is called an action potential
-the action potential is localized and last a very short time
The sodium potassium pump restores the membrane to its
original polarized condition by pumping sodium and potassium ions back to their original positions
The period of repolarization when the sodium potassium pump restores the membrane, which lasts a
few milliseconds, is called the refractory period, during which the neuron can’t respond to another stimulus
The refractory period ensures that an
impulse moves along an axon in one direction only since the impulse can move only to a region where the membrane is polarized
The first action potential generates a second action potential which
generates a third, and so on
The impulse moves along the axon
propagating itself without losing any strength
-if the axon is myelinated, the impulse travels faster
The action potential is ‘all or nothing’
either the stimulus is strong enough to cause an action potential or it’s not
How does the body distinguish between a strong and weak stimulus?
by the frequency of action potentials
-a strong stimulus sets up more action potentials than a weak one does
An impulse travels along an axon ______, it crosses a synapses ________.
electrically, chemically
The cytoplasm at the terminal branch of the neuron
contains many vesicles, each containing 100s of molecules of neurotransmitter
Depolarization of the presynaptic membrane causes
Ca++ ions to rush into the terminal branch through calcium-gated channels
What does the sudden rise in Ca++ levels do to vesicles?
stimulates the vesicles to fuse with the presynaptic membrane and release the neurotransmitter by exocytosis into the synapses, which sets up another action potential on the adjacent cell
What happens after a neurotransmitter released into a synapse?
destroyed by an enzyme that stops the impulse at that point
What are the most common neurotransmitters?
acetylcholine, serotonin, epinephrine, norepinephrine, dopamine, and GABA
Many cells release the gas _____ to stimulate other cells
NO nitric oxide
Eye
cones
photoreceptors in the retina that distinguish different colors
Eye
cornea
tough, clear covering that protects the eye and allows light to pass through
Eye
humor
fluids that maintain the shape of the eyeball
Eye
iris
colored part of the eye that controls how much light enter the eye
Eye
lens
focuses light onto the retina
Eye
pupil
small opening in the middle of the iris
Eye
retina
converts light into nerve impulses that are carried to the brain
Eye
rods
photoreceptors in the retina that are extremely sensitive but don’t distinguish different colors
Ear
auditory canal
ear canal, where sound enters
Ear
cochlea
fluid-filled part of inner ear, sends nerve impulses to brain
Ear
ear bones
hammer, anvil, and stirrup;
transmit vibrations from eardrum to oval window
Ear
eustachian tube
equalizes pressure between environment and inner ear
Ear
oval window
sends waves of pressure to the cochlea
Ear
Semicircular canals
fluid filled, helps you maintain your balance
Ear
tympanum
ear drum, vibrates as sound waves hit it
Excretion removes
CO2 and water from cell respiration and nitrogenous wastes from protein metabolism
Organs of excretion
skin, lungs, liver, and kidneys
Skin excretes
sweat consisting of water and salts, including urea
Lungs excrete
water vapor and CO2 from the Krebs cycle
Liver doesn’t excrete
any substances from the body but its the site of deamination of amino acids and the production of urea
Kidneys excrete
excess water and urea
Kidney adjusts both the
volume and the concentration of urine depending on the animal’s intake of water and salt and the production of urea
the kidneys are supplied by blood from
renal artery
The kidneys filter about
1,500 liters of blood per day and produce on average 1.5 liters of urine
Why is the kidney able to respond quickly to the changing requirements of the body?
its under hormonal control
A major hormone, ADH _______, is released by the
antidiuretic hormone
posterior pituitary and targets the collecting tube of the nephron
ADH regulates
blood pressure by controlling how much water is reabsorbed by the kidneys
Nephron
basic functional unit of the kidney
consists of a cluster of capillaries known as the glomerulus-which sits inside a cuplike structure called Bowman’s capsule, a long narrow tube called the tubule, and the loop of Henle
Each human kidney contains about
1 million nephrons
The nephron carries out its job in 4 steps
filtration
secretion
reabsorption
excretion
Filtration in the kidney occurs by
diffusion
it’s passive and non-selective
The filtrate contains everything small enough to
diffuse out of the glomerulus and into Bowman’s capsule including glucose, salts, vitamins, wastes such as urea, and other small molecules
From the bowman’s capsule, the filtrate travels into the
loop of Henle and then the collecting duct or tubule
From the collecting tubule, the filtrate trickles into the
ureter and the urinary bladder for temporary storage and then to the urethra and out of the body
Secretion is the
active, selective uptake of molecules that didn’t get filtered into Bowman’s capsule
-this occurs in the tubules of the nephron
Reabsorption is the process by which most of the
water and solutes (glucose, amino acids, and vitamins) that initially entered the tubule during filtration are transported back into the capillaries and thus back to the body
Where does reabsorption occur?
in the tubule, the loop of Henle, and the collecting tubule
-the longer the loop of henle, the greater the reabsorption of water
Everything that passes into the collecting tubule
is excreted from the body
The 3 types of muscle are
smooth
cardiac
skeletal
Smooth or involuntary muscle
- makes up the walls of blood vessels and the digestive tract
- doesn’t have a striated appearance
- under the control of the autonomic nervous system
Skeletal or voluntary (striated) muscles
- very large and multinucleate
- work in pairs, 1 muscle contracts while the other relaxes
- biceps and triceps are one pair
Cardiac muscle
- found in the heart and is striated like skeletal muscle
- generates its own action potential
- individual heart cells will beat on their own, even when removed from the body
Within the cytoplasm of each skeletal muscle cell
are 1000s of fibers called myofibrils that run parallel to the length of the cell
Myofibrils consist of
thick and thin filaments
Each thin filament consists of
actin proteins
Each thick filament is composed of
myosin proteins
How do muscles contract?
when thick and thin filaments slide over each other
