2. • NERVOUS SYSTEM
•Rapid communication by neural mechanisms
• ENDOCRINE SYSTEM
•less rapid communication by hormonal
mechanisms
3.
4. • Originated from irritability – a
fundamental property of life;
the ability to respond to
environmental stimuli
• Neural signaling has higher
specificity and is relatively
faster than hormonal
signaling.
• Some nerve impulses travel at
120 meters per second (about
400 km/h)
• Basic plan is to:
1. Receive information from both
external and internal
environments
2. Encode this information
3. Transmit this information
5. • Neuron – functional unit of nervous systems
– has many types depending on function and location
– transmit nerve signals to and from the brain
6. • Cell body (or soma) – has nucleus
• Dendrites – branch from the cell body
The soma and dendrites are the neuron’s receptive apparatus.
• Axon – a long fiber, may be meters in length in the largest
mammals
– conducts nerve signal
In vertebrates and some complex invertebrates, the axon is
often covered with myelin – an insulating sheath that
accelerates transmission
– consists of 70-80% lipids and 20-30% protein
• Nodes of Ranvier – parts of the axon that are not coated with
myelin
• Axon terminals – transmitters
• Synapse – gap between axon terminals and the receiving cell
7. Neuroglial Cells (or simply glial cells) – surround neurons
• Schwann’s cells – manufactures myelin in the peripheral
nervous system
• Oligodendrocytes – manufacture myelin in the central
nervous system
• Astrocytes – star-like shape
– serve as nutrient and ion reservoirs for neuron
– provide scaffold during brain development
– essential for regenerative process
• Microglial cells – smaller than astrocytes
– essential for regenerative process
8.
9. • Afferent (or Sensory) Neurons – connected to receptors
• Receptors function to convert external and internal environmental
stimuli into nerve signals which are carried by afferent neurons into the
CNS
• Efferent (or Motor) Neurons – carry nerve signals to
effectors
• Effectors are organs, tissues, or cells that become active upon
stimulation.
• Interneurons – interconnect neurons
11. • In vertebrates, nerve processes (usually axons) are often
bundled together in a wrapping of connective tissue to form a
nerve.
• Cell bodies of these nerve processes are located either in the
central nervous system or in ganglia (bundles of nerve-cell
bodies located outside CNS)
12. • Nerve Net – forms an extensive network in and under the
epidermis all over the body
– radially symmetrical animals, sea anemones,
hydras, jellyfishes, comb jellies, etc
13. • Bilateral Nervous System
• Flatworms have the simplest bilateral nervous system
14. • Bilateral Nervous
System
• Annelids’ nervous system
consist of a bilobed brain,
a double nerve cord with
segmental ganglia and
distinct afferent and
efferent neurons
15. • Bilateral Nervous
System
• Molluscan nervous
system
• Vary among groups
• Squids and octopi have
well-centralized
nervous systems
16. • Bilateral Nervous
System
• The nervous system of
arthropods resembles the
annelids’, but arthropods
have larger ganglia and
better developed sense
organs
• Mushroom bodies –
brain region associated
with learning; largest in
social instects
17. Vertebrates
• Encephalization – the
process of the great
elaboration of size,
configuration, and
functional capacity of the
brain
• Fast responses
• Great capacity for information
storage
• Enhanced complexity and
flexibility of behavior
• The ability to form
associations between past,
present, and (at least in
humans) future events
20. • Early vertebrates had three (3) principal brain
divisions:
1. Prosencephalon or forebrain – smell
2. Mesencephalon or midbrain – vision
3. Rhombencephalon or hindbrain – hearing and
balance
24. • Human brain is the most complex, even though it is not
the largest nor the most convoluted.
• Contains 35 billion neurons, each of which may receive information
from 10 000 synapses at one time
• May be so complex that it will never be able to understand its own
function!
25. • Spinal cord – long, tubular bundle
of nerves extending from the brain
• Wrapped in three layers of membranes
called meninges
• Two (2) Zones:
1. Zone of Gray Matter – inner zone
– butterfly shaped
– consists of the cell bodies of motor
neurons and interneurons
2. Zone of White Matter – outer zone
– contains bundles of axons and
dendrites linking different levels of the
cord with each other and with the brain
26.
27. Three (3) Major
Functions:
1. Conduit for motor
information
Motor information travel
down
2. Conduit for sensory
information
Sensory information travel up
3. Center for
coordination of
29. 1. Sensory (or Afferent) Division
• brings sensory information to the central nervous
system
2. Motor (or Efferent) Division
• conveys motor commands to muscles and glands
• Two (2) Components of the Efferent Division
1. Somatic Nervous System – skeletal muscles
2. Autonomic Nervous System – smooth muscles,
cardiac muscles, glands
• Two (2) Subdivisions of the Autonomic Nervous
System
1. Parasympathetic System
30.
31.
32.
33.
34. • Composed of glands that produce hormones
that regulate metabolism, growth and
development, tissue function, sexual function,
reproduction, sleep, and mood, among other
things
• Hormonal signaling is relatively much slower
than neural signaling.
• Endocrine control is expected when a sustained
effect is required.
35. • Hormones – chemical messengers
– chemical compounds released into the
blood in small amounts and transported by the
circulatory system throughout the body to distant
target cells
– may act as a neurotransmitter or as a
parahormone
• Endocrine glands – small, well-vascularized ductless
glands
• Target cell – where a hormone initiate physiological
responses
36.
37.
38.
39. • Neurosecretory cells – specialized nerve cells capable of
synthesizing and secreting hormones
- principal source of hormones in many metazoan
phyla
• The most common hormones among different invertebrate
groups are peptides and neuropeptides.
• Cardioactive peptide – increases heart rate in crustaceans
• Crustacean hyperglycaemic hormone family (CHH) –
regulate metabolism in crustaceans
• Adipokinetic hormone family – regulate metabolism in
insects
• Molting and metamorphosis are primarily controlled by the
interaction of these two hormones:
1. Molting hormone or ecdysone
41. • Hypothalamus – contains
groups of neurosecretory cells
that manufacture releasing
hormones and/or release-
inhibiting hormones
• These hormones then either
stimulate or inhibit release of various
anterior pituitary hormones.
• Pituitary gland (or hypophysis)
– a two-part gland
1. Anterior Pituitary
(adrenohypophysis)
2. Posterior Pituitary
(neurohypophysis) – connected
to the hypothalamus by a stalk
called infundibulum
42. • Pineal Gland – produces the hormone melatonin
• Melatonin secretion is strongly affected by the presence of light.
• Lowest during daylight hours, highest at night
• In nonmammalian vertebrates, the pituitary gland is
responsible for maintaining circadian rhythms – 24-hour long
rhythms; a circadian rhythm serves as a biological clock for
many physiological processes that follow a regular pattern
• In mammals, the suprachiasmatic nucleus (an area of the
hypothalamus) is the primary circadian pacemakers, although
the pineal gland still produces melatonin nightly and serves to
reinforce the circadian rhythm of the suprachiasmatic nucles.
43.
44. • Thyroid gland – a large endocrine gland located in the neck
of all vertebrates
• Triiodothyronine (T3) and Thyroxine (T4)
• Most important functions:
• Promote normal growth and development of the nervous system of
growing animals
• Stimulate metabolic rate
45. Three (3) Hormones that Maintain Blood Calcium Level:
1. Parathyroid hormone (PTH) – stimulates release of calcium
when blood calcium level decreases from normal level
- produced by the parathyroid
glands
2. 1,25-dihydroxyvitamin D3 – active calcium absorption by
the gut
- hormonal form of vitamin D3
3. Calcitonin – protects the body against blood calcium level
increase
- produced by thyroid gland
46.
47. • Adrenal Gland – composed of the cortex (outer region of
adrenocortical cells) and medulla (inner region of specialized
cells)
• Corticosteroid hormones are classified in two (2) groups:
Long-term stress responses
1. Glucocorticoids – influence food metabolism, inflammation, and stress
• include cortisol and corticosterone – gluconeogenesis
2. Mineralocorticoids – regulate salt balance
• include aldosterone which promotes tubular reabsorption of sodium
and tubular secretion of potassium by the kidneys
• Hormones secreted by adrenal medullary cells:
• Epinephrine (adrenaline)
• Norpinephrine (nonadrenaline)
These hormones and the sympathetic nervous system have the same
general effects on the body.
• “Fight or flight” (short-term stress) responses
48. • Pancreas – both an exocrine and an endocrine organs
• Islets of Langerhans – small islets of tissue scattered within the exocrine
portion
• Several hormones are secreted by different cell types within
the islets:
• Beta cells – insulin (promotes entry of glucose into body cells; lowers
blood glucose level) and amylin
• Alpha cells – glucagon (increases blood glucose level)
• Delta cells – somatostatin (inhibit secretion of other pancreatic
hormones)
• Gamma cells – pancreatic polypeptide (reduces appetite)
49.
50. • Gonads:
• Testes (male)
• Ovary (female)
• Gonads produce most of the body’s sex hormones:
androgens, estrogens, progestins, etc.
51. • Tropic hormones – hormones that influence the action of
another hormone or an endocrine gland
