Download Essentials of Biology Sylvia S. Mader

Essentials of Biology
Sylvia S. Mader
Chapter 27
Lecture Outline
Prepared by: Dr. Stephen Ebbs
Southern Illinois University Carbondale
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
27.1 Nervous System
• The nervous system and endocrine
system work cooperatively to regulate the
body’s activities.
• These systems use chemical signals
called hormones to exert this control.
27.1 Nervous System (cont.)
The Human Nervous System
• The human nervous system has two parts.
– The central nervous system (CNS) consists of
the brain and spinal cord.
– The peripheral nervous system (PNS)
consists of the nerves outside the central
nervous system.
• The nerves of the central nervous system
(CNS) are paired, meaning that there is
one on each side of the body.
The Human Nervous System (cont.)
• There were five evolutionary advances that lead
to the complexity of the human nervous system.
– The CNS is capable of summarizing incoming
messages before sending an outgoing one.
– Nerve cells are specialized in role.
– The brain has centers that control specific activities.
– The CNS is connected to the body by peripheral
nerves.
– Complex sense organs have evolved.
Neurons
• The nerve cells, or neurons, of the
nervous system have three parts.
– The cell body is the main part of the cell.
– The dendrite receives impulses.
– The axon sends impulses.
• The axons of some neurons have a myelin
sheath for protection.
Neurons (cont.)
Neurons (cont.)
• There are three types of neurons.
– Sensory neurons receive impulses from
sensory receptors and transmit them to the
CNS.
– Interneurons form bridges between different
parts of the CNS to integrate activities and
perform higher function.
– Motor neurons transmit signals from the CNS
to muscles and glands to stimulate their
function.
The Nerve Impulse
• The ability of neurons to transmit nerve impulses
depends upon a difference in charge across the
cell membrane.
• The interior of neurons is more negatively
charged compared to the outside.
• The transmission of a nerve impulse along a
neuron involves a rapid, self-propagating
reversal of this negative charge along the
membrane (an action potential).
The Nerve Impulse (cont.)
• This action potential is generated by the rapid
exchange of ions through channels in the
membrane.
– Sodium atoms rush in to reverse the charge.
– Potassium atoms exit to restore the charge.
• If myelin is present on the axons the propagation
of the action potential differs.
– For unmyelinated neurons, the action potential in one
area triggers the potential in an adjacent area.
– For myelinated neurons, the action potential moves
by saltatory conduction, jumping between nodes.
The Nerve Impulse (cont.)
The Nerve Impulse (cont.)
The Synapse
• In the CNS, the axon of one neuron and the
dendrite of the next is separated by a gap called
the synapse.
• In the PNS, this gap at a neuromuscular junction
is called a synaptic cleft.
• The transmission of the nerve impulse from one
neuron to the next is achieved by the release of
chemicals into the synapse.
– Acetylcholine
– Norepinephrine
The Synapse (cont.)
Drug Abuse
• Recreational drugs alter the action of
neurotransmitters in the body.
– Some drugs, such as cocaine, are stimulants,
causing nerve excitation.
– Chemical depressants, such as heroin and
marijuana, decrease excitation by binding to
specific receptors.
The Central Nervous System
• The organization of the animal brain differs
significantly between species, but can be divided
into three zones.
– The forebrain, which is highly developed in humans
– The midbrain
– The hindbrain
• The spinal cord provides the communication
between the brain and PNS.
The Central Nervous System (cont.)
The Brain
• The cerebrum of the brain coordinates
activities of other parts of the brain.
• The cerebrum is divided into halves and
has a core of white matter covered by the
outer gray matter (cerebral cortex).
• Areas within the cerebrum are devoted to
specific functions.
The Brain (cont.)
• The diencephalon consists primarily of the
thalamus and hypothalamus.
– The hypothalamus regulates functions such as
hunger, thirst, and body temperature.
– The thalamus receives sensory input from all senses
except smell.
• The cerebellum receives sensory input and
routes motor impulses from the cerebral cortex
to the skeletal muscles to produce movement.
The Brain (cont.)
• The brain stem, which consists of several
structures, regulates involuntary functions
in the body such as heartbeat and
breathing.
– Midbrain
– Pons
– Medulla oblongata
The Brain (cont.)
The Brain (cont.)
The Limbic System
• The limbic system is a network that
includes the diencephalon, cerebrum,
hippocampus, and amygdala.
• The limbic system integrates higher
mental functions and base emotions.
• The hippocampus and amygdala are
critical for learning and memory.
The Limbic System (cont.)
• There are different types of memory.
– Semantic memory provides recollection of
numbers and words.
– Episodic memory recalls events.
– Skill memory provides memory of learned
motor tasks.
The Limbic System (cont.)
The Peripheral Nervous System
• The peripheral nervous system (PNS) consists
of nerves, which is a collection of axons from
many neurons.
• The primary components of the PNS are the
twelve cranial nerves which connect the PNS to
the brain.
• The PNS also has 31 pairs of spinal nerves
containing many sensory and motor axons.
The Somatic System
• The somatic system of the PNS involves the
nerves that convey sensory information to the
CNS and the motor nerves that transmit
impulses to muscles.
• Voluntary control of skeletal muscles is provided
by the brain.
• Involuntary response, or reflexes, can be
mediated by the brain or the spinal cord.
The Somatic System (cont.)
The Autonomic System
• The autonomic system provides involuntary
control of glands, cardiac muscle, and smooth
muscle.
• This system has two divisions which have motor
axons in the same organs, but have opposite
effects.
– The sympathetic division mediates the so-called “fight
or flight” responses.
– The parasympathetic division mediates processes
during the resting state.
The Autonomic System (cont.)
27.2 The Endocrine System
• The endocrine system involves the gland
that secrete the body’s hormones into the
bloodstream.
• The endocrine system works with the
nervous system to provide homeostasis in
the body.
27.2 The Endocrine System
(cont.)
The Action of Hormones
• Hormones trigger their effect in cells that have
the proper receptor for that hormone.
• Steroid hormones pass directly through the cell
membrane and directly binds to DNA to alter
gene expression.
• A peptide hormone binds to a receptor on the
membrane surface, triggering the release of a
second messenger that triggers the response.
The Action of Hormones (cont.)
The Action of Hormones (cont.)
Hypothalamus and Pituitary Gland
• The hypothalamus regulates the internal
environment through the autonomic nervous
system.
• The hypothalamus controls the hormonal
secretions of the pituitary gland.
• The pituitary gland has two regions.
– The anterior pituitary
– The posterior pituitary
Hypothalamus and Pituitary Gland
(cont.)
• The anterior pituitary secretes several
hormones.
– Thyroid-stimulating hormone stimulates the release of
thyroxine and triiodothyronine.
– Adrenocorticotropic hormone stimulates the release of
glucocorticoid by the adrenal cortex.
– Gonadotropic hormones stimulate the reproductive
glands.
– Prolactin stimulates the mammary glands during
pregnancy.
– Growth hormone stimulates growth.
Hypothalamus and Pituitary Gland
(cont.)
• The posterior pituitary produces two
hormones.
– Antidiuretic hormone controls the water
balance of the urine and bloodstream.
– Oxytocin is responsible for uterine
contractions during childbirth and milk letdown
during infant nursing.
Thyroid and Parathyroid Glands
• The two hormones produced by the thyroid
gland, thyroxine and triiodothyronine, help
regulate metabolic rate throughout the body.
• These two hormones require iodine to function
properly.
• Goiter is a disease caused by over- or
underproduction of thyroid hormones.
Calcium Regulation
• The thyroid also produces calcitonin,
which helps to regulate calcium levels in
the bloodstream.
• When calcium levels drop too low, the
parathyroid releases parathyroid hormone,
which triggers the release of calcium from
bones and the reabsorption of calcium in
the kidneys.
Adrenal Glands
• The adrenal glands are associated with
the kidneys and consist of two regions.
– The inner portion is the adrenal medulla.
– The outer portion is the adrenal cortex.
• The hypothalamus controls the activities of
the adrenal glands, signalling them to
release their hormones in time of stress.
Adrenal Medulla
• The adrenal medulla produces hormones
that mediate short-term responses to
stress.
– Epinephrine (adrenaline)
– Norepinephrine (noradrenaline)
Adrenal Cortex
• The adrenal cortex produces two hormones that
mediate long-term responses to stress.
– Mineralocorticoids such as aldosterone regulate salt
and mineral levels.
– Glucocorticoids such as cortisol regulate
carbohydrate, fat, and protein metabolism.
• Hyposecretion of these hormones can lead to
potentially fatal Addison’s disease.
• Hypersecretion of hormones produces Cushing’s
syndrome.
Adrenal Cortex (cont.)
Pancreas
• The pancreas is composed of two types of
tissues.
– The exocrine tissues produce digestive juices that are
released into the small intestine.
– The endocrine tissues consists of tissues called
pancreatic islets.
• The pancreatic islets produce and secrete
insulin and glucagon to regulate sugar levels in
the blood.
Pancreas (cont.)
Diabetes Mellitus
• Diabetes is a hormonal disease that
develops when the body cells do not take
up and/or metabolize glucose.
• There are two types of diabetes.
– In Type I diabetes, the pancreas fails to
produce insulin.
– In Type II diabetes, insulin is produced, but
the body’s cells fail to respond to it.