Stage 1 Biology Endocrine and Nervous System

Lets get thinking… What factors does the body need to control/coordinate? What are the consequences of not being able to control these factors? What do we mean when we say someone has quick reflexes? What about when we say certain behaviour is due to stress?

Response systems A stimulus (change) in the environment is detected by receptors (“nerve endings”) in the body. The body may respond though the nervous system, endocrine system or a combination of both of the systems

Some important receptors Photo-receptors (sensitive to light) Special structures making up the retina of the eye, attached to the optic nerve. 4

Some important receptors Sound Receptors : Vibrating air causes the ear drum to transfer vibrations to the middle ear bones (malleus, incus and stirrup) and then to fluid in the cochlea. This moves hairs attached to the auditory nerve. 5

The Hormonal System Involves hormones (a chemical compound secreted by an endocrine gland ) which are secreted into the blood There are two types of hormones: – Steroid hormones (lipid based) – Peptide Hormones (peptide based)

The Endocrine System The endocrine system regulates mood, growth and development, tissue function, and metabolism, as well as sexual function and reproductive processes. The endocrine system is in charge of body processes that happen slowly, such as cell growth whilst faster processes are controlled by the nervous system.

Hormones As the body's chemical messengers, hormones transfer information and instructions from one set of cells to another. Each hormone affects only the cells that are genetically programmed to receive and respond to its message. Hormone levels can be influenced by factors such as stress, infection, and changes in the balance of fluid and minerals in blood.

Glands… A gland is a group of cells that produces and secretes chemicals Some types of glands release their secretions in specific areas. For instance, exocrine glands, such as the sweat and salivary glands, release secretions in the skin or inside of the mouth. Endocrine glands, on the other hand, release more than 20 major hormones directly into the bloodstream where they can be transported to cells in other parts of the body.

The Hypothalamus A collection of specialised cells that is located in the lower central part of the brain. Provide a link between the nervous and endocrine system Nerve cells in the hypothalamus control the pituitary gland by producing chemicals that either stimulate or suppress hormone secretions from the pituitary. Although it is no bigger than a pea, the pituitary gland, located at the base of the brain just beneath the hypothalamus, is considered the most important part of the endocrine system. It's often called the "master gland" because it makes hormones that control several other endocrine glands.

The pituitary gland The Pituitary Gland: Some of the hormones produced….. growth hormone, which stimulates the growth of bone and other body tissues and plays a role in the body's handling of nutrients and minerals prolactin, which activates milk production in women who are breastfeeding endorphins, chemicals that act on the nervous system to reduce sensitivity to pain. hormones that signal the ovaries and testes to make sex hormones. The pituitary gland also controls ovulation and the menstrual cycle in women. antidiuretic hormone which helps control body water balance through its effect on the kidneys and urine output oxytocin which triggers the contractions of the uterus that occur during labor.

The thyroid Located in the front part of the lower neck, is shaped like a bow tie or butterfly and produces the thyroid hormones. These hormones control the rate at which cells burn fuels from food to produce energy. Thyroid hormones also play a key role in bone growth and the development of the brain and nervous system in children. Attached to the thyroid are four tiny glands that function together called the parathyroids. They release parathyroid hormone, which regulates the level of calcium in the blood.

Pineal gland The pineal body, also called the pineal gland, is located in the middle of the brain. It secretes melatonin, a hormone that may help regulate the wake-sleep cycle.

Reproductive hormones The testes, secrete hormones called androgens, the most important of which is testosterone. These hormones regulate body changes associated with sexual development (eg: growth spurt, deepening of the voice, growth of facial and pubic hair, increase in muscle growth, production of sperm) The ovaries produce eggs and secrete the female hormones estrogen and progesterone. Estrogen is involved in the development of female sexual features such as breast growth, the accumulation of body fat around the hips and thighs, and the growth spurt that occurs during puberty. Both estrogen and progesterone are also involved in pregnancy and the regulation of the menstrual cycle.

The pancreas Produces insulin and glucagon. They work together to maintain a steady level of glucose, in the blood.

How do hormones work? Receptors are stimulated A hormone is secreted by a gland Hormone travels in blood to target cell Bind to a protein cell receptor on target cell This binding initiates a message inside the cell which brings about a effect

Try this Complete Questions From text page 119 Q1-4 on the endocrine system!

The Nervous System The electrical ‘message’ transmitted by nerve cells. Nerve impulses regulate many body functions including: – Glands – Heart Rate – Breathing rate – Body Temperature – Reflexes

Nerve transmission Receptors are stimulated A message is sent via a sensory neuron to the CNS (central nervous system) The CNS works out what to do via interneurons Nerve impulses are sent via motor neurons to the muscle or gland to initiate a response!

Neurons Neurons come in many sizes. For example, a single sensory neuron from your fingertip has an axon that extends the length of your arm, while neurons within the brain may extend only a few millimeters. Neurons have different shapes depending on what they do.

The neuron Neurons have three basic parts: Cell body: This main part has all of the necessary components of the cell, such as the nucleus (which contains DNA). Axons: Long, thin, cable-like projections of the cell carry nerve impulses along the length of the cell. Axons can be covered with a thin layer of myelin, which is made of fat. Dendrites (nerve endings): Small, branch-like projections of the cell make connections to other cells and allow the neuron to communicate with other cells or perceive a stimuli.

The Nervous System

Reflexes A rapid-involuntary response to a stimulus Does not involve the brain

Knee-Jerk Reflex

Comparing Hormonal and Nervous transmission

Try this…. Page 119 text– Questions 5, 6 and 9 Reaction time investigation