Understanding Nerve Impulse Transmission and the Endocrine System

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Nerve Impulse Transmission Across a Synapse

The nerve impulse which has been transmitted along the membrane of the transmitter neuron reaches the end of its axon. At the end of the axon, the arrival of the nerve impulse causes neurotransmitters to be released into the synaptic cleft. Neurotransmitters bind to the membrane of the receptor neuron and generate a new nerve impulse. The new nerve impulse is transmitted along the membrane to the axon, where the whole process is repeated.

The Autonomic Peripheral Nervous System

The autonomic PNS consists of motor nerves which regulate the activity of the internal organs and control involuntary movements. The autonomic nervous system is divided into the sympathetic nervous system and the parasympathetic nervous system. The sympathetic nervous system causes the body to relax. These two systems are antagonistic.

Reflex Actions

Reflex actions are fast, involuntary, automatic responses that are controlled by the spinal cord and are triggered in emergency situations.

How Endocrine Works?

1. The hypothalamus regulates the pituitary gland: The hypothalamus reacts to both external stimuli and variations in the concentration of hormones in the bloodstream. This reaction consists of sending nerve signals to the pituitary gland, stimulating it to manufacture hormones. 2. The pituitary gland regulates the other glands: When stimulated by the hypothalamus, the pituitary glands start manufacturing hormones. The hormones of the pituitary gland enter the bloodstream and travel round the body. Some affect organs while others regulate the secretion of different hormones in the various glands of the endocrine system. 3. Hormones regulate the activity of the body's organs: The hormones produced by glands are distributed through the bloodstream and regulate the activity of the body's organs. 4. Hormones halt secretion in the pituitary gland: An increase in the level of hormones in the bloodstream sends a signal to the pituitary gland, telling it to stop manufacturing its hormones.

Purpose of the Skeletal System

- To serve as an internal framework for our bodies - To protect organs and internal tissues - To provide an anchorage support for muscles - To manufacture blood cells - To serve as a reserve store of calcium and phosphorus

Types of Muscle

- Fusiform: such as the triceps and biceps in the arm. Their ends may be divided into 2, 3, or 4 branches, in which case they are called biceps, triceps, or quadriceps. - Flat: such as the pectoral muscles which move the arms forward. - Circular: such as the orbicularis oris muscle which opens and closes the lips.

Male Reproductive System

- The testes are 2 glands situated in a pouch of skin called the scrotum. Made up of many tiny tubes called seminiferous tubules. The testes produce testosterone and, from puberty onwards, spermatozoa. Newly formed spermatozoa are infertile and cannot move. - The epididymis stores the spermatozoa while they mature. - The vasa deferentia connect the epididymis to the urethra. - The accessory glands manufacture secretions which, along with spermatozoa, make up semen. The glands are seminal vesicle which are located behind the urinary bladder and lead to the vasa deferentia and the prostate which is shaped like a chestnut and is located at the point where the urethra leaves the urinary bladder. Also, there is Cowper's gland which lead to the urethra and are located underneath the prostate. The function of the penis is to deposit spermatozoa in the female reproductive system. It is formed by erectile tissue which engorges when blood is sent to it, causing the penis to stiffen or become erect. Its head is protected by a fold of skin known as the foreskin.

The Formation of Spermatozoa

Takes place in the seminiferous tubules, which includes the interstitial that segregate testosterone. The walls of these tubules contain cells called germ cells, which are constantly multiplying themselves. As they multiply, the cells move towards the end of the tube and gradually mature until they become spermatozoa. The process is initiated at puberty by the action of male hormones and continues throughout the rest of the individual's life.

Female Reproductive System

- The ovaries are a pair of glands located at the bottom of the abdominal cavity, on either side of the uterus. They produce ova and female sex hormones. - The genital tracts are - the fallopian tubes that connect the ovaries to the uterus. Their purpose is to catch the ova released by the ovaries and transport them to the uterus, where fertilization took place. - The uterus is a hollow, muscular organ inside which the embryo develops. The fallopian tubes lead into its upper part, while its lower part known as the cervix connects to the vagina. - The vagina is an elastic tube which connects the uterus to the outside of the body. It is here that spermatozoa are deposited. - The external genitalia are formed by the labia which are basically folds of skin, and the clitoris. The labia minora surround the openings of the vagina and the urethra.

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