The Human Endocrine And Nervous System

The Brain

The brain is protected by the skull and is made up of soft tissue, which includes grey and white matter, containing nerve cells, non-neuronal cells, and small blood vessels (Medical News Today, 2018). The brain controls the thoughts, memory, speech, and movements of the body, such as arms, legs, and organs. The brain and spinal cord are the bodies central nervous system, the brain is the command centre for the body and the spinal cord is the pathway for messages by the brain to the body and from the body to the brain. (Mayfield Clinic, 2020)

• Skull
• Cerebellum
• Spinal cord
• Meninges
• Cerebrum

Spinal Cord

The spinal cord is protected by the vertebral columns and is made up of bundles of nerve fibres. It runs down from the brain through a canal in the centre of the bones of the spine. These bones protect the spinal cord, like the brain, the spinal cord is covered by the meninges and cushioned by cerebrospinal fluid (Neurosurgery, 2020). The spinal cord consists of nerves that carry incoming and outgoing messages between the brain and the rest of the body. If the spinal cord is injured, the exchange of information between the brain and other parts of the body is disrupted.

The Peripheral Nerves

The peripheral nervous system is made up of nerves that branch off from the spinal cord and extend to all parts of the body. Unlike the brain and spinal cord, the peripheral nerves are not protected by the skull or vertebral column, which leaves it exposed to toxins and mechanical injuries. The peripheral nerves consists of the nerves and ganglia, the main function of the PNS is to connect the CNS to the limbs and organs, essential serving as a relay between the brain and spinal cord and the rest of the body (Teach Me Physiology, 2020)

Autonomic Nervous System Parts

The Autonomic nervous system is a control system that acts largely unconsciously and controls bodily functions. It divides in two, the sympathetic division, which is associated with the fight of flight responses and the parasympathetic division, which refers to by the epithet of rest and digest. Homeostasis is the balance between the two systems (Lumen, Unknown date)

The Reflex arc

Throughout the body, neurons have special proteins in their membrane called receptors, receptors respond to signals in the environment, some receptors respond to pressure. Sensory receptors in the ears respond to vibrations in the air that are interpreted as sound, and receptors in the eyes to respond to light. Interneurons are the middleman of the nervous system, they connect sensory input to other cells that required for action, in a reflex arc, the sensory neurons send signals to the interneuron and activates it, the interneuron then relays that signal to the next neuron, a motor neuron. The motor neuron connects with interneurons in the spinal cord, they send messages from the central nervous system to the body. The motor neurons run out of the spinal cord and connect with a muscle. Motor neurons, like sensory neurons, can be long, connecting the spinal cord with the most distant appendage. (Study, 2020)

Most nerve pathways have cells that communicate with each other by means of neurotransmitters. A neurotransmitter is released from one presynaptic membrane, onto the postsynaptic membrane. Excitatory presynaptic cells release neurotransmitters that make that postsynaptic membrane more excitable and more likely to generate nerve impulses. (Micheal kent, 2000). An action potential is the mode through which a neuron transports electrical signals. It is defined as a brief change in the voltage across the membrane due to the flow of certain ions into and out of the neuron (Teach me Physiology, 2020). Transmission of a signal within a neuron (in one direction only, from dendrite to axon terminal) is carried out by the opening and closing of voltage-gated ion channels, which cause a brief reversal of the resting membrane potential to create an action potential (Biology, 2020)

In an electric synapse, ions move directly from one neuron to another via gap junctions, the membrane depolarization associated with an action potential in the presynaptic cell passes through the gap junctions, leading to a depolarization, and thus an action potential, in the postsynaptic cell. An action potential travels down the axon of the per-synaptic, sending cells and arrives at the axon terminal. The axon terminal is adjacent to the dendrite of the post-synaptic, receiving cell. This spots of close connection between axon and dendrite is the synapse An electric synapse, ion pass directly from the per-synaptic cell to the post-synaptic cell through gap junction. These synapses are much less common than chemical synapses. Impulse transmission at chemical synapses occurs with a small-time delay but is nearly instantaneous at electric synapses.

Pineal Gland

The pineal gland produces melatonin, a serotonin-derived hormone which modulates sleep patterns in both circadian and seasonal cycles. The hormones produced control so many different processes in the body. It senses the bodies needs and sends signals to different organs and glands throughout the body to regulate their functions and maintain an appropriate environment (Your Hormones, Unknown date)

Hypothalamus and Pituitary gland

The pituitary gland in the brain is known as a master gland, it secretes serval hormones into the blood in response to the bodies condition, such as blood water levels. These hormones can also act on other glands to stimulate the release of different type of hormones and bring about effect (BBC bite size, 2020). The hypothalamus is based at the base of the brain next to the pituitary.

The Thyroid parathyroid and Gland

The thyroid gland is a small butterfly-shaped gland which sits in front of the trachea. One of its main function is to produce hormones that help regulate the bodies metabolism, which helps turn food into energy. These hormones are called triiodothyronine (T3) and thyroxine (T4) (NHS, 2020). The parathyroid gland sits behind the thyroid gland, it plays the role in regulating the bodies levels of the minerals, calcium, and phosphorus.

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The thymus

Thymus is a small organ located behind the breastbone, its hormones are called thymosin, they are generally small protein, which regulates the development and selection of an immune-competent repertoire of T cells, and stimulate antibody production by B cells. Unlike most organisms it is at its largest in children, and once they reach puberty, the thymus starts to slowly shrink and become replaced by fat (Very well health, 2020)

The Adrenal Gland

The adrenal glands are small glands located on top of each kidney. They produce hormones that the body can not live without, including hormones such as, cortisol and aldosterone. Cortisol helps the body respond to stress and has many other important functions. With adrenal gland disorder, the gland in the body makes to much or not enough hormones (Medline Plus, 2020)

The Ovaries

The ovaries are located in the lower abdomen of a female. The ovaries produce and release eggs (oocytes) into the female reproductive tract at the mid-point of each menstrual cycle. They also produce the female hormones oestrogen and progesterone. Oestrogen stimulates female characteristics at puberty and controls a woman’s reproduction cycle. Progesterone prepares the endometrium for the potential of pregnancy after ovulation, it triggers the lining to thicken to accept a fertilized egg. (Hormones health, 2020).

The Testes

The testes are two small organs that are found inside the scrotum, next to the penis, they have two functions, to produce sperm and to produce a hormone called testosterone. Testosterone is a sex hormone that plays important roles in the body. In men, it is thought to regulate sex drive (libido), bone mass, fat distribution, muscle mass and strength, and the production of red blood cells and sperm (National Institutes of Health, 2013)

Lipid hormones, such as steroid hormones diffuse across the membrane of the endocrine cell, which are released into the blood stream and carried via the blood to the target cells. Peptide hormones are a class of proteins which are bound by receptor proteins and enable of disable a biological pathway.

Peptide hormones are mostly water-soluble and can travel freely in the blood because it is similar to the blood’s consistency. However, they are repelled by lipid or fatty structures such as the membrane that surround the cell and nucleus (E.hormones, Unknown date). Hormones are released into the bloodstream through which they travel to target sites. The target cell has receptor specific to a given hormone and will be active by either a lipid- soluble, or water-soluble hormone (Lumen, Unknown date).

The pituitary glad is referred to as the master gland because it monitors and regulates many of the bodies functions through hormones that it produces. It is connected by a stalk to a part of the brain called the hypothalamus, together, the brain and pituitary gland form the neuroendocrine system. This system constantly monitors glands and organs to determine whether to send or to stop the chemical messages or hormones that control their functions (Barrow, Neurological Institute, 2020)

When a threat is perceived, the sympathetic nerve fibres of the autonomic nervous system are activated. This leads to the release of certain hormones from the endocrine system. A major action of these hormones generates the fight or flight response (Britannica, 2020). The endocrine system works together with the nervous system to influence many aspects of human behaviour, including the fight or flight response. The nervous system can respond quickly to stimuli, through the use of action potentials and neurotransmitters. Response to nervous system stimulation are typically quick but short lived. The endocrine system responses to stimulation by secreting hormones into the circulatory system that travels to the target tissue (Medicine, 2020)

The hypothalamus is a section of the brain that controls thermoregulation. When it senses the internal temperature becoming too low or high, it sends signals to the muscles, organs, glands, and nervous system. It then responds in a variety of ways to help return the bodies temperature to normal (Health line, 2017) when the hypothalamus senses the body is getting to hot, it will send signals to the bodies sweat glands to make the body sweat and cool itself off. When it sense that the body is too cold, it will send signals to the muscles that make the body shiver and create warmth, this is called maintaining homeostasis (ASU for you, unknown date).

The autonomic division of the nervous system modulates the release of insulin and glucagon. Glucagon is a hormone found in the alpha cells of the islet in the pancreas, which is a polypeptide, which raises blood glucose concentration (Micheal Kent, 2000). The sympathetic stimulation that occurs with exercise stimulates glucagon production and this maintains blood-glucose levels that would otherwise fall as muscles use glucose for this energy. Regulation of blood glucose is largely done through the endocrine hormones of the pancreas, a balance of hormones achieved through a negative feedback loop. The main hormones of the pancreas that affect blood glucose include insulin, glucagon, someatostain and amylin (ATrain, 2020). Insulin is a hormone found in the beta cells of the isles which is a protein, it lowers the blood glucose concentration in the body. (Micheal Kent, 2000).

Reference

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