Hormones

In the body there are eight major endocrine glands. Every gland secretes particular hormone.
Hormones are transported in extra cellular fluid to help regulates the cellular function. It regulates the metabolic function.

Nervous system

The nervous system is composed of central nervous system and peripheral nervous system

Parts of Brain and its Function

Cerebrum, Cerebellum, and medulla oblongata constitute the brain.

Medulla oblongata: -

It involves in involuntary functions, such as regulation of heartbeat, breathing, vasoconstriction, and reflex centers for vomiting, coughing, sneezing, swallowing, and hiccuping. Homeostasis of body is maintained by hypothalamus. Thirst, hunger, body temperature, water balance etc are regulated by it and also connects the nervous system to endocrine system.

Mid brain and pons also involved in involuntary functions. The thalamus serves as central relay point for incoming nervous message.

Cerebellum: -
Muscles co- ordination and maintenance of normal muscle tone and posture is done by cerebellum. Actually it co-ordinate balance of body

Cerebral Hemisphere: -
Sensory and motor functions are regulated by cerebral hemisphere. Intelligence and reasoning, learning and memory are governs by it.

Spinal cord: -
Carries message to and away from brain. It also involves in reflex action.

Peripheral nervous system: -

Consist of nerves, which connect brain and spinal cord to rest of body.

Cranial nerves: -
Take impulses from body to brain and from brain of body

Spinal nerves: -
They take impulses to, and away from spinal cord. Somatic nervous system comprises of sensory and motor neuron.

Sensory neuron: -
Sensory receptor detect the state of body or state of surrounding
Five types of sensory receptor

1) Mechanical receptor: -

Detect mechanical deformation of the receptor or of cells adjacent to the receptor.

2) Thermo receptor: -

Detect change in temperature like cold and warmth.

3) Nociceptor: -

Detect damage in the tissue whether it is physical or chemical damage.

4) Electromagnetic receptor: -

Detect light on retina of eye.

5) Chemo receptor: -

Detect taste, smell, oxygen level, osmolality, carbondioxide concentration, and other factor that make up chemistry of body.

Autonomic nervous system

A large segment of nervous system is called autonomic nervous system. It operates at a subconscious level and controls many function of internal organs including action of heart, movements of gastrointestinal tract and secretion by different gland and helps in urinary bladder emptying, sweating, body temperature and many other activities. This system is activated mainly by centers located in spinal cord, brainstem, and hypothalamus.
The autonomic signals are transmitted to the body through two major subdivisions: -
1) Sympathetic
2) Parasympathetic

1. Sympathetic nerve fiber:-
   Sympathetic nerve originates in spinal cord between the segment T1 and L2 and pass first in to sympathetic chain then in to the tissue and organ. Sympathetic nerve fibres in skeletal nerves control the blood vessels, sweat glands, and pilo erector muscle. The sympathetic pathway originating in different segments of the spinal cord are not necessarily distributed to the same parts of the body as spinal nerves fibres from the same segment. Instead the sympathetic fibres From T1 goes to head
   From T2 goes to neck
   From T3 T4 T5 T6 goes to thorax
   From T7 T8 T9 T10 T11 goes to abdomen
   From T12 L1 L2 goes to legs
   This distribution is only approximate and overlaps generally.
2. Parasympathetic nerve fibre: -
   Parasympathetic nerve fibre originates from central nervous system through several cranial nerves, second and third spinal nerves, and occasionally the first and fourth sacral nerves. Almost 75% of parasympathetic nerves are in the vagus nerve distributed in entire thoracic and abdominal regions of the body. Parasympathetic nerve in third nerve goes to papillary sphincters and ciliary muscles of eye. Seventh nerve fibres passes to lacrimal and sub mandibular glands and fibres from ninth nerve pass to the parotid gland.
   The sacral parasympathetic fibres congregate are called pelvic nerves, leaves the sacral plexus on each side of cord and distribute their fibres to descending colon, rectum, bladder and lower portions of ureters. Also this group of parasympathetic supplies fibres to external genitalia.
   Functions of sympathetic and parasympathetic nerves fibres: -
   Acetylcholine and adrenaline are two types of synaptic transmitters are there secreted by nerve endings of parasympathetic and sympathetic nerve fibres. Those fibres, which secrete acetylcholine, are called cholinergic. Those fibres, which secrete adrenaline or norepinephrine, are called adrenergic. Preganglionic neurons of both parasympathetic and sympathetic fibres are cholinergic. Therefore, acetylcholine when applied to ganglia will excite postganglionic neurons of parasympathetic and sympathetic nerve fibres. The postganglionic neuron of parasympathetic fibres secretes acetylcholine. It means they are cholinergic. While most of postganglionic neurons of sympathetic fibres are adrenergic, through sympathetic nerve fibres to the sweat glands, pilo erector muscles and few blood vessels are cholinergic.
   Those hormones act on different organs to cause the respective parasympathetic and sympathetic effect.

Circulatory system: -

The circulatory system is a continuous system like closed circuit.
The circulation of blood in body is by two ways
a. Pulmonary circulation
b. Systemic circulation

1. Pulmonary circulation: -
   Due to the contraction of right ventricle of heart, blood pumps out from right ventricle to pulmonary artery, this opens in the lungs. Gaseous exchange takes place in lungs. Then the oxygenated blood through Pulmonary veins enters in left atrium of the heart.
2. Systemic circulation: -
   Oxygenated blood from left atrium goes in to left ventricle. Left atrium, on contraction, pumps the blood in to left ventricle through martial valve. Then the left atrium relaxed and left ventricle contracts and pumps the blood in to the aorta that divided in to different arteries. Arteries distributed the blood to different parts of the organs and there they divided in to arterioles and then in to capillaries.

The functional part: -
Arteries: - They transport blood under high pressure to tissue. They are made up of strong vascular walls. Blood flows rapidly in the arteries.
Arterioles: - Arterioles have strong muscular walls, that is capable of closing the arterioles completely or allow it to be dilate several folds. Arterioles have capability of altering blood flow to the capillaries. Arterioles are last small branches of arterial system through which blood is released in to capillaries.
Capillaries: - Capillaries walls are very thin and are permeable to small molecular substances, their function is to exchange fluid, nutrients electrolyte, hormone and other substance between blood and interstitial spaces.
Venules: - They collect blood from capillaries and gradually coalesce in to progressively larger veins.
Veins: - They transport blood from tissues back to heart.

Lymphatic

Lymphatic system is a necessary route by which fluid can flow from interstitial spaces in to the blood. They carry proteins of high molecules and large particulate matter away from tissue spaces, which are not removed by absorption directly in to the blood capillaries. This removal is an absolutely essential function without which we would die in 24 hrs.
Lymph is derived from interstitial fluid that flows in to the lymphatic.
Factors determine rate of lymph flow

• Interstitial fluid pressure
  Elevation of Interstitial free fluid pressure above its normal level (-5.3mm of Hg) results in increase in flow of interstitial fliud in to lymphatics capillaries. Thus increase rate of lymph flow. The factors responsible for elevation in lymphatic pressure are
  1. Elevated capillary pressure.
  2. Decrease plasma colloid osmotic pressure.
  3. Increase interstitial fluid protein.
  4. Increase permeability of capillaries.
• Lymphatic Pump
  1. Intrinsic pumping.
  2. Extrinsic pumping.
• Lymphatic capillary pump.

Core temperature

Skin

Skin consist of three layers
1. Epidermis: - Uppermost layer forming the surface of skin made up of cells called keratinocytes, melanocytes and langerhan cells are another important feature of epidermis.
   This layer is useful for protection and pigmentation.
2. Dermis: - This is a dense connective tissue, which is responsible for pliability and mechanical resistance, and regulation of body temperature It contains
   1. Blood vessels: - It supplies nutrition and oxygen to cells of skin helps in Thermoregulation.
   2. Meissner's corpuscles: - These are touch receptor. Detects light touch and soft.
   3. Pacinians corpuscles :- These are receptor for deep pressure and vibration.
   4. Free nerve endings: - They are sensitive to pain, temperature changes and itchiness.
   5. Nerves fibers: - They forward the information.
   6. Sebaceous gland: - It secretes oily substance called sebum, which is a natural moisturizer that conditions the hair and skin.
   7. Sweat glands: - These are sweat producing structures involved in thermoregulation they excretes some salts like ammonia and metabolic by products.
   8. Hair follicles :- They helps in closing up of skin pores and keeping the warmth in.
   9. Lymphatic vessels: - They help to protect the body against foreign invaders or infections.
3. Hypodermis: - Hypodermis: - Hypodermis strongly impacts the skin to the body but allows its restricted movements. It provides the protective cushion and insulates the body.