CONTROL AND INTEGRATIONNERVOUS & ENDOCRINE SYSTEMS

Introduction• NERVOUS SYSTEM•Rapid communication by neural mechanisms

• ENDOCRINE SYSTEM• less rapid communication by hormonal mechanisms

The world revealed by our senses is exclusive to us humans, and we share this with no other animal.

(Idea was first conceived by Jakob von Uexkull, a German biologist)

NERVOUS SYSTEM

NERVOUS SYSTEM• 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 environments2. Encode this information3. Transmit this information4. Process this information for

appropriate action

NERVOUS SYSTEM

• Neuron – functional unit of nervous systems – has many types depending on function and location – transmit nerve signals to and from the brain

Parts of a Neuron• Cell body (or soma) – has nucleus• Dendrites – branch from the cell bodyThe soma and dendrites are the neuron’s receptive apparatus.

• Axon – a long fiber, may be meters in length in the largest mammals

– conducts nerve signalIn 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

Parts of a NeuronNeuroglial 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

Classifications of Neurons• 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

Stimulus

Receptor

Sensory

Neuron

CNS

Motor Neuro

nEffect

or

Nervous System• 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)

Evolution of Nervous Systems• 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

Evolution of Nervous Systems• Bilateral Nervous System• Flatworms have the simplest bilateral nervous system

Evolution of Nervous Systems• Bilateral Nervous

System• Annelids’ nervous system consist of a bilobed brain, a double nerve cord with segmental ganglia and distinct afferent and efferent neurons

Evolution of Nervous Systems• Bilateral Nervous

System•Molluscan nervous system • Vary among groups• Squids and octopi

have well-centralized nervous systems

Evolution of Nervous Systems• 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

Evolution of Nervous SystemsVertebrates• 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

CENTRAL NERVOUS SYSTEM• Composed of the spinal cord and the brain

The Brain• 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

The Brain

Pons

The Brain• 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!

The Spinal Cord• 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

The Spinal Cord

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 certain reflexes

PERIPHERAL NERVOUS SYSTEM• Composed of all nerves not included in the CNS

Two (2) Functional Divisions of the PNS

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

Division1.Somatic Nervous System – skeletal

muscles2.Autonomic Nervous System – smooth

muscles, cardiac muscles, glands• Two (2) Subdivisions of the Autonomic

Nervous System1. Parasympathetic System2. Sympathetic System

ENDOCRINE SYSTEM

Endocrine System• 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.

Endocrine System• 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

• Parahormones – stimulate cell growth or some biochemical process

Invertebrate Hormones• 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 ecdysone2. Juvenile hormone

Vertebrate Endocrine Glands and Hormones• The major human

endocrine glands

Hormones of the Hypothalamus and Pituitary Gland• 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 gland1. Anterior Pituitary

(adrenohypophysis) 2. Posterior Pituitary

(neurohypophysis) – connected to the hypothalamus by a stalk called infundibulum

Biorhythms• 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.

Hormones of Metabolism• 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

Hormonal Regulation of Calcium Regulation

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

Hormones of the Adrenal Cortex and Medulla

• 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 responses1. 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

Hormones of the Islet Cells of the Pancreas

• 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)

Hormones of the Gonads• Gonads:• Testes (male)• Ovary (female)

• Gonads produce most of the body’s sex hormones: androgens, estrogens, progestins, etc.

Tropic Hormones• Tropic hormones – hormones that influence the

action of another hormone or an endocrine gland