PHYSIOLOGY
WEEK 3
BASICS OF COMMUNICATION AND CONTROL: ENDOCRINE SYSTEM
1.1. Describe the basic mechanisms used by the body for communication and control of
body systems and distinguish the general functional features of neural control (rapid
responses) vs endocrine control (slower processes)
BASICS OF CELL COMMUNICATION
Cell-Cell Communication
● Cells must communicate with each other
○ Maintain body homeostasis
○ Bring about coordinated changes in body
physiology
● Communication induced by extracellular signal
molecules that can act locally, over short or long
distances
● Cell grow, divide, or die according to the signals they
receive
Mechanisms of Cell Communication
1) Local communication/short range
● Directed communication/contact dependent
○ Chemical message diffuses locally to target tissue
○ Effects limited to adjacent interconnected cells of same type
ions, small solutes
● Through extracellular fluid
○ Effects primarily limited to local area; target cells must have
appropriate receptors
, ● Across synaptic clefts (local communication)
○ Neuronal (synaptic) below
■ Neurotransmitters = chemical
messengers released by nerve cells
that diffuse across synaptic cleft to activate target cell postsynaptic
receptors
■ Allows the transmission of signals from one neuron to the next across
synapses
■ Note: effects limited to very specific area
■ Very fast but brief transmission
2) Long distance communication
● Through circulatory system
○ Target cells are primarily in other tissues and must have appropriate
specific receptors, eg, hormones
THE ENDOCRINE SYSTEM
Endocrine vs Exocrine Glands
● Glands = body structures which produce and secrete chemicals into
ducts or the blood
○ Formed by folds of epithelial tissue
, ● Endocrine glands secrete their products - hormones - directly into the bloodstream
○ Ductless glands
● Exocrine glands secrete their products into ducts that carry these
products to other organs or outside body
○ Usually control short term activity
○ Eg, sweat glands, gallbladder
○ Note: pancreas endocrine + exocrine
The Endocrine System
What are the main differences between the nervous and endocrine systems?
Interactions Between the Nervous System and the Endocrine System
Responsible for controlling the synthesis, release and levels of many circulating hormones
, CONTROL OF HORMONAL RELEASE AND BIOLOGICAL EFFECTS
How is release of hormones triggered?
● Hormonal stimulus
○ Eg, thyroid hormone release stimulated by pituitary TSH
● Neural stimulus
○ Nerve impulses stimulate hormone release
○ Typically under the control of the sympathetic nervous
system
■ Eg, adrenaline secreted by adrenal medulla regulates the response to
immediate stress (fight or flight)
WEEK 3
BASICS OF COMMUNICATION AND CONTROL: ENDOCRINE SYSTEM
1.1. Describe the basic mechanisms used by the body for communication and control of
body systems and distinguish the general functional features of neural control (rapid
responses) vs endocrine control (slower processes)
BASICS OF CELL COMMUNICATION
Cell-Cell Communication
● Cells must communicate with each other
○ Maintain body homeostasis
○ Bring about coordinated changes in body
physiology
● Communication induced by extracellular signal
molecules that can act locally, over short or long
distances
● Cell grow, divide, or die according to the signals they
receive
Mechanisms of Cell Communication
1) Local communication/short range
● Directed communication/contact dependent
○ Chemical message diffuses locally to target tissue
○ Effects limited to adjacent interconnected cells of same type
ions, small solutes
● Through extracellular fluid
○ Effects primarily limited to local area; target cells must have
appropriate receptors
, ● Across synaptic clefts (local communication)
○ Neuronal (synaptic) below
■ Neurotransmitters = chemical
messengers released by nerve cells
that diffuse across synaptic cleft to activate target cell postsynaptic
receptors
■ Allows the transmission of signals from one neuron to the next across
synapses
■ Note: effects limited to very specific area
■ Very fast but brief transmission
2) Long distance communication
● Through circulatory system
○ Target cells are primarily in other tissues and must have appropriate
specific receptors, eg, hormones
THE ENDOCRINE SYSTEM
Endocrine vs Exocrine Glands
● Glands = body structures which produce and secrete chemicals into
ducts or the blood
○ Formed by folds of epithelial tissue
, ● Endocrine glands secrete their products - hormones - directly into the bloodstream
○ Ductless glands
● Exocrine glands secrete their products into ducts that carry these
products to other organs or outside body
○ Usually control short term activity
○ Eg, sweat glands, gallbladder
○ Note: pancreas endocrine + exocrine
The Endocrine System
What are the main differences between the nervous and endocrine systems?
Interactions Between the Nervous System and the Endocrine System
Responsible for controlling the synthesis, release and levels of many circulating hormones
, CONTROL OF HORMONAL RELEASE AND BIOLOGICAL EFFECTS
How is release of hormones triggered?
● Hormonal stimulus
○ Eg, thyroid hormone release stimulated by pituitary TSH
● Neural stimulus
○ Nerve impulses stimulate hormone release
○ Typically under the control of the sympathetic nervous
system
■ Eg, adrenaline secreted by adrenal medulla regulates the response to
immediate stress (fight or flight)
