Download pruitt_ppt_ch12

Human Physiology:
How Does the
Human Body Work?
Homeostatic Control System
How Do Parts of The body
Communicate?
• How does the body quickly send
information to anatomical structures?
• Diffusion of substances is effective for
short distances.
• However, moving information quickly over
long distances is the function of the
nervous system.
The Nervous System Provides
Rapid Communication
• Organization of the
nervous system
– Central nervous
system: brain and
spinal cord
– Peripheral nervous
system: nerves
The Nervous System Provides
Rapid Communication
• Functions of the nervous system:
– Thought, language, learning and
comprehension.
• Occurs at the brain
– Reflexes
• Controlled by spinal cord
The Nervous System Provides
Rapid Communication
• Two types of neurons:
– Sensory: receives
information about the
outside world or about
conditions in the body
and sends it to the
brain.
– Motor: brain sends
messages through
these neurons to
tissues and organs to
that affect a response
The Nervous System Provides
Rapid Communication
• Neurons conduct
electrical impulses
– To increase the speed
of conductance, axons
are insulated by
myelin sheaths
produced by Schwann
cells.
Action Potentials
• Form of electrical
impulses.
• Transient all-or-none
reversals in electrical
potential across a
neuronal membrane
that rapidly move
from dendrites, to cell
body, to axon.
Action Potentials
• Disruption of ion balance outside or inside the cell
causes membrane potential to reach threshold
which causes opening of sodium gated ion
channels.
– Allows sodium ions to enter cell and cause inside of the
cell to have + charge.
• This causes opening of potassium gated channels
which allows potassium to exit the cell.
– Returning the negative charge to the inside of the cell.
Synapses
• Junction between one neuron and another neuron
or muscle or gland.
• When the action potential travels to the end of the
neuron, it stimulates the release of
neurotransmitter (such as acetylcholine) into the
synapse.
• The neurotransmitter travels across the synapse
and binds to protein receptors on the membrane
of another cell.
– Can initiate another action potential.
Functional Divisions of the Nervous
System
• Two divisions:
– Somatic:
• responsible for our voluntary actions
– Autonomic:
• works to maintain our body’s homeostasis
independently of our conscious will.
• Two Types
– Sympathetic
– Parasympathetic
Endocrine System
• Second system for communication
– Works by means of hormones (chemicals)
which travel in the bloodstream to a distant
group of target cells where they render their
effect.
• Coordinates slower, more long-term
responses such as growth, maturation,
reproduction and water balance.
Endocrine System
• Target cells have specific receptors that
bind and recognize only that hormone.
• When a hormone binds, the target cell
responds in one of three basic ways:
– Change some aspect of the cells metabolism
– Influence the movement of substances across
the cell membrane.
– Turn gene expression on or off
• Altering protein synthesis
Hypothalamus and Pituitary Glands
• Found in the brain
– Control many vital functions of the body.
• Hypothalamus:
– Regulates temperature, water balance,
appetite, thirst, growth, waking, sleeping, and
reproduction.
• Pituitary has two divisions:
– Anterior and Posterior.
Posterior Pituitary
• Releases two hormone that are made in
hypothalamus and stored in posterior
pituitary gland
– Antidiuretic hormone (ADH)
• Causes body to conserve water and release less in
the urine.
– Oxytocin
• Induces contractions in the uterus needed for
childbirth
• Induces the release of milk from the breast.
Anterior Pituitary
• Hypothalamus produces releasing
hormones and release-inhibiting
hormones.
– These hormone are released into the blood
and travel a short distance to the anterior
pituitary gland
– Regulate the activities of the pituitary gland
Negative Feedback
• Serves as a mechanism for regulating the
release of hormones in the endocrine
system.
• Without negative feedback, a response
designed to bring some aspect of the body
back to homeostasis could easily
overcompensate.
– Pushing it in the opposite direction.
How Do Humans Acquire and Process
Nutrients and Get Rid of Wastes?
• If we were simple-celled organisms we
could acquire the nutrients we need
through diffusion across our membrane.
• Digestive, respiratory, circulatory, urinary
systems help us obtain the nutrients we
need as multicellular organisms.
Digestive Tract
• It is a long hollow tube that begins at the
mouth and ends at the anus.
• Function:
– Take in food, store it and prepare it to enter
the cells of the body.
• Need to digest proteins, carbohydrates and lipids
in order to for cells to use them as raw materials
and energy.
Processes involved in breaking
down and taking in food:
• Digestion: breaking down food into smaller
molecules using digestive enzymes.
• Secretion: release of digestive enzymes, acids,
and other substances that aid in digestion.
• Motility: movement of food and digestive
secretions through the digestive tract.
• Absorption: entry of simple molecules produced
by digestion across the digestive tract wall into
the blood and finally to the cells of the body.
Mouth and Esophagus
• Mouth:
– Beginning of the digestive tract
– Chewing occurs here
– Digestive enzymes in saliva start begin digesting
carbohydrates
• Esophagus:
– Tube that connects the mouth and the stomach
Stomach
• Functions:
– Stores food for a brief
time and moves it into
the intestines in small
amounts after it is
liquefied.
– Digestion of proteins.
– Acid in the stomach
also protects the body
against bacterial
invasion.
Stomach
• Peristalsis:
– Waves of muscular contractions that move the chyme
into the small intestines
• Chyme: liquified food
• Movement of food out of the stomach is
regulated by the pyloric valve
Intestines
• Are about 14 feet long with many twists
and turns.
– Inner wall surface area is over 100 feet.
• Important for increase absorption.
• Small intestines:
– Digestion occurs in its final stages here.
– Pancreatic enzymes help in digestion.
• Pancreas also release bicarbonate to neutralize
the acid from the stomach.
Liver
• Releases bile
– Stored in gallbladder.
– Mixture of bile salts and bicarbonate
• Bile salts emulsify fat (break it down into smaller
globules)
• Both pancreatic secretions and bile enter
the small intestines through the bile duct.
Movement in the Small
Intestines
• Segmentation
– Responsible for the
majority of muscle
movement in the small
intestines.
– Moves the chyme.
Absorption in the Small
Intestines
• Structure of the small intestines facilitates
absorption of food into the cells of the
small intestines.
– Molecules then move into the blood and
finally to the cells.
Absorption in the Small
Intestines
Large Intestines
• 5 feet of tubing
• All that remains of the chyme is
– indigestible material, water, bacteria, and a
few other things that could not be absorbed.
• Primary role:
– Store fecal material, absorb water from it and
propel it to the rectum.
Respiratory System
• Functions:
– Exchange oxygen and carbon dioxide.
– Regulate pH of the body.
– Used for vocalization.
– Protects the body form inhaled irritants or
pathogens.
Structure of Respiratory System
Ventilation
• Is the movement of air between the alveoli
and the environment
– When the diaphragm contracts, it allows air to
enter the lungs.
• Oxygen moves by diffusion into the oxygen-poor
blood.
– When the diaphragm relaxes, the air leaves
the lungs.
• Carbon dioxide diffuses from the blood into the air
spaces of the lung and is expelled.
Cardiovascular System
Cardiovascular System
• Consists of :
– Heart, arteries, capillaries, veins.
• Primary role of blood:
– is to transport substances to and from all
parts of the body.
• Moves nutrients, wastes, and chemical
messengers (hormones).
Heart
• Consists of four
chambers:
– 2 atria (atrium)
– 2 ventricles
• Has four valves:
– Bicuspid, Tricuspid
– Pulmonary, Aortic
Heart
• Consist two pumps
– Pulmonary Circulation:
• Blood travels from the heart to the lungs and back
to the heart.
– Systemic Circulation:
• Blood travels through arteries to capillaries to veins
and back to the heart.
Heartbeat
• Pacemaker cells
– Found in the right atrium in the region of the
sinoatrial node.
– Initiates electrical impulses.
• Passes to all the other cells in the heart.
• Responsible for initiating contraction of the heart
muscle.
Urinary System
• Removes metabolic
wastes.
• Consists of:
– Kidneys and urinary
bladder.
• Functional unit is the
nephron.
– Over a million in each
kidney.
Nephron
• Cleanse the blood
and use three
processes to do so:
– Filtration
– Reabsorption
– Secretion
Nephron
• A protein-free, cell-free filtrate of the blood
enters the nephron tubule at one end.
• As the filtrate moves through the nephron
tubule substances such as sodium
chloride, water and glucose are removed.
• Other substances such as potassium ions,
hydrogen ions and drugs are added to the
filtrate from the blood.
Nephron
• Effect of hormones on urine production:
– ADH
• Causes the body to retain water
–Preventing it from showing up in the
urine
• Causes urine concentration to increase
How Does the Human Body
Move?
• Muscles exert a force that causes
movement
• Three types of muscle in the body:
– Skeletal: attached to bones
– Cardiac: heart muscle
– Smooth: tissue that surrounds hollow organs
Skeleton Provides the
Framework
• Cartilage
– Primary component of
baby skeleton.
– Persists in adults in
places where firmness
and flexibility are
needed.
Skeleton Provides the
Framework
• Bone
– Mostly made of a
calcium-rich matrix
that exists outside of
cells.
Skeleton Provides the
Framework
• Ligaments
– Are strong, flexible bands that connect
cartilages or bones together at points of
attachment called joints.
• Tendons
– Attach skeletal muscle to bones.
– Are tough bands of white connective tissue.
Muscle Provides Movement
• Muscles cause movement by contracting
• Muscle tissue is organized at many
different levels
– Muscles are composed of fibers
• Each fiber is a single cell.
Muscle Provides Movement
Muscle Provides Movement
• Muscle fibers contain two proteins
– Actin: thin protein
– Myosin: thick protein
• When these two fibers slide past one
another, muscle contraction occurs.
• Process is fueled by ATP.
Muscle Provides Movement
Role of the action potential in
muscle contraction
• Action potentials are
the stimulus that
initiates muscle
contraction.
• Action potentials
cause muscle to
release calcium from
sarcoplasmic
reticulum.
– Calcium interacts with
actin to cause muscle
contraction.
How Do Humans Reproduce?
• They reproduce sexually by a process that
requires coordinated activities of the male
and female reproductive systems
• Both systems produce gametes through
the process of gametogenesis
– Meiosis is a component of this process.
– Occurs in woman’s ovaries and men’s testes.
How Do Humans Reproduce?
• Gametogenesis in
both sexes is
influenced by
hormones released
from the brain and the
gonads.
Male Reproductive Tract
• LH and FSH
– Released from the pituitary.
– Stimulate gonads to produce gametes and
testosterone.
• Testosterone is required for gametes to mature
– Also responsible for secondary sex characteristics in
men.
Male Reproductive Tract
Female Reproductive Tract
• Gametogenesis occurs before birth.
– Only one egg reaches maturity during monthly
cycle.
• Ovaries contain follicles.
– Small sac-like structures holding one egg
(oocyte) surrounded by accessory cells.
• The menstrual cycle allows for maturation
and release of the egg.
Female Reproductive Tract
Menstrual Cycle
• Cycle begins with menstruation.
– Sloughing of the endometrium.
• Cycle is marked by a mid-month event.
– Ovulation: Single egg is released from the
ovary.
• All of these events are regulated by
changes in different levels of sex
hormones.
Menstrual Cycle
Pregnancy
• Egg is fertilized by a sperm on its way to
the uterus.
– Forms a zygote
• Zygote begins dividing, becoming an
embryo.
• Embryo may implant in the endometrium,
resulting in pregnancy.
How Does the Body Fight
Disease?
• Human body is challenged by pathogens.
– Disease-causing microbes
• Bacteria and viruses are most common type
• The function of the immune system is to
protect you from the disease causing
organisms.
– Immunity is a combination of generalized nonspecific defenses and highly specific defenses
against particular invaders.
Immune system
• Tissues that affect the
immune system
response are
scattered throughout
the body
– Main cells of the
immune system are
leukocytes
• Produced in bone
marrow and mature in
thymus
Immune system
• First line of defense:
– Shields that create barriers.
• Examples: skin, stomach, and mucous layers of
respiratory and digestive tracts.
– These defense make it difficult for invaders to
gain access to the internal compartments of
the body.
Cells of the Immune System
Immune system
• Second line of defense:
– Nonspecific inflammatory response that
occurs at the site of infection.
• Phagocytic leukocytes
– engulf invaders
– Attract more immune cells to the site.
• Chemical defenses include
– the release of histamines
– Release of other chemicals that kill the cells directly
Immune system
• Third line of defense:
– Most powerful line of defense directed at pathogens
that have been encountered more than once.
– First encounter:
• Lymphocytes that produce antibodies that recognize an
invader antigen are stimulated to proliferate and produce
more antibodies
• Some of the progeny become memory cells that remain in
the lymphoid tissue,
– ready to make antibodies in the event that the same antigen is
encountered in the future