Human bio Year 12 semester 1 exam revision

Define the endocrine system

A group of glands that secrete hormones

Define Hormone

Chemicals that are secreted into the blood to be transported around the body

How can hormones affect the function of cells

Hormones can affect the function of cells by changing the type, activities or quantities of proteins produced

What can hormones affect

All cells of the body, only particular groups of cells and only particular organs

How do hormones affect enzymes

Hormones can change the concentration or activity of enzymes

What are the characteristics of steroid hormones

Lipid soluble, long lasting effects, bind to transport proteins to travel through blood towards target cell, hormone separates from transport proteins and diffuses across cell membrane, binds to receptor protein inside cytoplasm or nucleus, forms hormone which activates or inhibits transcription for protein synthesis

Proteins and Amines hormone

Water soluble, quick acting, short lasting effect, attach to a receptor protein on the cell membrane, a secondary messenger diffuses through the cell and activates specific enzymes

Enzyme amplification

A causcading effect where the number of reaching molecules is increased hundreds or thousands of times for each step of the pathway

Hormone clearance

After a hormone has produced the desired effect, it is broken down by the liver and kidney and excreted in bile or urine

Location of hypothalamus

The hypothalamus is located at the based of the brain

Location of pituitary gland

The pituitary gland lies under the hypothalamus and is joined by a stalk called the infundibulum

Describe the roles of the hypothalamus

Has roles in both the nervous and endocrine system, connects the two systems, regulates body temperature, water balance, heart rate, secretes releasing factors that stimulate the secretion of hormones, secretes inhibiting factors that slow the release of some hormones

Describe the function of the pituitary gland

Anterior and posterior lobes function separately

Where is the anterior lobe located

Anterior lobe is connected to the hypothalamus via blood vessels through the infundibulum

Where is the posterior lobe located

The posterior lobe is connected to the hypothalamus via nerve fibers

Describe the functions of the anterior lobe of the pituitary gland and the hormones it secretes

Releasing and inhibiting factors secreted by the hypothalamus

What hormones does the anterior lobe secrete

FSH, LH, GH, TSH, ACTH

What does FSH do

Stimulates development of the follicle in the ovaries or production and maturation of sperm in the testes

What does LH do

Brings an ovulation and forms corpus luteum after ovulation in the ovaries and stimulates interstitial cells in the testes to secrete testosterone

What does GH do

Stimulates body growth, particularly the skeleton. Increases rate of amino acids build into proteins, maintains size of organs once maturity is reached

What does TSH do

Stimulates the production of hormones from the thyroid gland

What does ACTH do

Controls production and release of hormones from adrenal glands

Describe the function of posterior lobe

Does not make hormones, hormones are made in nerve cells in the hypothalamus of the brain and the hormones travel down the extensions of the nerve cells into the posterior lobe are stored ready for secretion. Release hormones are triggered by nerve impulses

What hormones does the posterior lobe secrete

Oxytocin and ADH

What does oxytocin do

Stimulates the contraction of muscles of the uterus and is released in large amounts during labor

What does ADH do

Helps retain water by causing the kidneys to remove water from urine

Where is the pineal gland located

Found deep inside the brain. About the size of a pea and decreases overtime

Function of the pineal gland

Secretes melatonin. Melatonin is stimulated by darkness and inhibited by light

Function of melatonin

Regulates sleep patterns

Location and structure of thyroid gland

Below the larynx and made of 2 lobes that wrap around the trachea

Function of thyroid gland

Secretes hormones in response to thyroid stimulating hormone, secretes 80% thyroxine and 20% triiodothyronine, thryoxine is longer lasting, regulates catabolic and anabolic reactions to cause release of energy and heat

Describe the function of calcitionin

Regulates calcium and phosphate in the blood

Describe the structure of the parathyroid gland

Four or more glands the size of peas

Describe the function of the parathyroid gland

Releases parathyroid hormone or parathormone

Describe the function of the parathyroid hormone

Increases calcium levels in the blood and phosphate excretion in urine

Describe the location of the thymus

Above the heart behind the sternum. Largest in young children and shrinks overtime

Describe the function of the thymus

Secretes thymosins

Function of thymosins

Influence the maturation of T-Lymphocytes

Describe the structure and location of the adrenal glands

Two glands above the kidney. Each gland has an adrenal medulla and adrenal cortex

Describe the function of the adrenal medulla

Adrenal medulla produces adrenaline and noradrenaline

Describe the function of adrenaline

Adrenaline prepares the body for a reaction to a threatening situation

Describe the function of noradrenaline

Noradrenaline is similar but has a particular effect of increasing rate and force of heartbeat

Describe the function of the adrenal cortex

Adrenal cortex produces 20+ hormones called cortiosteroids

Function of aldosterone

Aldosterone acts on kidneys to reduce sodium and increase potassium in urine

Function of cortisol

Cortisol promotes normal metabolism, repair tissues and helps the body withstand stress

Describe the location and structure of the pancreas

15cm long and lies below the stomach. Is both an endocrine and exocrine organ

Describe the exocrine and endocrine function of the pancreas

Exocrine function is it secretes digestive enzymes via a duct. Endocrine function is it produces and secretes hormones

Describe the structure and location of the islets and langherans

Islets and langerhans are clusters of specialists cells found in the pancreas

Beta cells

Secrete insulin which decreases blood sugar levels

Alpha cells

Secretes glucagon which increases blood sugar levels

Testosterone

Development and maintenance of male sex characteristics

Oestrogen

Development and maintenance of female sex characteristics and regulate the menstural cycle

Progesterone

Regulates the menstural cycle and pregnancy, prepares glands for milk secretion

What is a neuron

The basic structural and functional units of the whole neuron system. Highly specific and designed for rapid communication of messages in the body

What is the structure of a neuron

Vary in size but all consist of a cell body and dendrites + axon

Structure of cell body

Contains the nucleus and is responsible for controlling the functioning of the cell

Structure of dendrites

Fairly short extensions of the cytoplasm of the cell body. Often highly branched and they carry nerve impulses into the cell body

Structure of axon

A single long extension of the cytoplasm. Usually carries nerve impulses away from the body

Structure of myelin sheath

Most axons are covered with a layer of material called the myelin sheath

Structure of axon terminal

At the axon end it divides into many small branches which terminate at the axon terminal

What are schwann cells

Outside the brain and spinal cord, the myelin sheath, called nodes of ranvier

What are the nodes of ranurer

At intervals along the axon are gaps in the myelin sheath

What are the three important functions of the myelin sheath

It acts as an insulator, it protects the axon from damage, speeds up the movement of nerve impulses along the axon

What is the Neurilemima

The outermost coil of the schwann cell forms a structure called the neurilemma around the myelin sheath. This structure helps in the repair of injured fibers

What is the neuromuscular junction

A specialized chemical synapse where a motor neuron terminal meets a skeletal muscle fiber acting as the site for transmitting electrical signals that trigger muscle contraction

What are sensory neurons

Sensory neurons carry messages from receptors in the sense organs, or in the skin, to the central nervous

What are motor neurons

Motor neurons carry messages from the central nervous system to the effectors, the muscles and glands

What are inter-neurons

Located in the central nervous system and are the link between sensory and motor neurons

What is a nerve

Outside the brain and spinal cord, nerve fibers are grouped together to form a nerve

Define electrochemical signal

Within a neuron, nerve impulses travel as electrochemical signals

Define ion

Ions in different concentrations existion each side of the membrane

Which two ions play a key role in generating an action potential

Potassium ions and sodium ions

What is the sodium potassium pump

Protein embedded in cell membrane that maintains the difference in ion concetration across the cell

How does a sodium potassium pump work

Uses ATP to pump 3 sodium ions out of the cell and 2 sodium ions in

What is a synapse

A synapse refers to the site where a neuron connects to another cell

What is a neurotransmitter

A small chemical which transfers a nerve impulse from one neuron to another

What is a receptor

A structure that is able to detect a change in the body’s internal or external envrionment

Thermoreceptor

Are able to respond to heat and cold

Skin thermoreceptors

Inform the brain of changes in the temperature outside the body

Osmoreceptor

Located in the hypothalamus are sensitive to even very small changes in osmotic pressure

Chemoreceptor

They are present in the nose, making vs sensitive to odours, and in the mouth giving us sensitivity to tastes

Touch receptor

Found mainly in skin, occurs in greater concentrations in areas such as lips, fingertips and eyelids

Pain receptors

Stimulated by damage to the tissues, occur in most organs but not the brain

What is a reflex

An action potential without conscious thought, in response to a particular stimulus

What is a reflex arc

A neural pathway that controls a reflex action

Meninges

Inside the bones and covering the surface of the brain and spinal cord are three layers of connective tissue forming membranes called the meninges

Dura mater

The outermost layer, the dura mater is tough and fiborus and therefore provides a layer of protection for the brain

Arachnoid mater

The middle meningeal layer, the arachnoid mater, is a loose mesh of fibrers

Pia mater

The inner layer, the pia mater is for more delicate, it contains many blood vessels and sticks closely to the surface of the brain and spinal cord

Cerebrospinal fluids

Third protective structures is cerebrospinal fluid, which occupies a space between the middle and inner layer of menninges

Cerebrospinal fluid three functions

Protection the CSF acts as a shock absorber, cushioning any blows or shock the CNS may sustain, support the brain is suspended inside the cranium and floats in the fluid that surrounds it, transport takes nutrients to the cells of the brain and spinal cord carries away their wastes

Cerebrum structure

Largest part of the brain, surface folded into convolutions

Cerebral hemisphere

Is divided into 4 lobes frontal, temporal, occipital and pariteal lobes

Cerebrum function

Cerebral cortex is involved in mental activities such as thinking, reasoning, learning, memory, intelligence and sense of responsibility. Also concerned with perception of the senses and the initiation and control of voluntary muscle contraction

Corpus callosum structure

A wide band of nerve fibers that lies underneath the cerebrum at the base of the longitudinal fissure

Corpus callosum function

Nerve fibers in the corpus callosum cross from one cerebral hemisphere to another and allow two sides of the cerebrum communicate with each other

Cerebellum structure

Lies under the rear part of the cerebrum. It is the second largest part of the brain and it’s structure is folded into a series of parallel ridges. Outerfolded part is grey matter inside is white matter which branches to all parts of the cerebellum

Cerebellum function

The cerebellum exercises control over posture, balance and the fine coordination of voluntary muscle movement. To carry out these functions the cerebellum receives sensory information from the inner ear for information about posture and balance

Structure of hypothalamus

Lies in the middle of the brain and cannot be seen from the outside

Functions of the hypothalamus

Regulation of heart rate, blood pressure, secretion of digestive juices, movement of the alimentary canal and the diameter of the pupil in the eyes, body temp, food and water intake, patterns of waking and sleeping, contraction of urinary bladder, emotional response, the secretion of hormones and coordination of parts of the endocrine system