Revision PPT Notes Flashcards
What is a Mutation?
Change in the sequence of DNA bases
Name the two types of Mutations and give definition
Substitution: One base replaced with another
Deletion: One base removed from the sequence
Can Mutations be beneficial?
Yes because randomly-occurring mutations sometimes result in a new allele being formed
Some can be beneficial as it could enable an or be better adapted than before.
How does Natural Selection work?
- Organism with an advantageous allele have higher survival chance
- They survive and reproduce, passing advantageous allele to offspring
- Next Generation have higher proportion of advantageous allele
- Next generation have higher survival chances, reproduce and pass on advantageous allele
- Frequency of advantageous allele increases from generation to generation
- Over time (through generations) this leads to evolution
Explain Negative Feedback Loop
Optimum Conditions
Change from optimum
Receptor detects change
Communication system tells effector
Effector reacts to reverse change
Return to Optimum conditions
What happens when Blood Glucose Level Rises?
Beta cells in Pancreas detect rise in Blood Glucose Level
They respond by producing Insulin directly into Blood Plasma
This is done by:
- Insulin binding to glycoprotein receptors on cell body surface membrane, stimulate cells to take in more glucose
- Insulin bind to glycoprotein receptors on Liver cells, stimulate liver to release enzymes that catalyse the conversion of glucose to glycogen
What happens when Blood Glucose Level Decreases?
Alpha cells in Pancreas detect decrease in Blood Glucose level
They respond by producing Glucagon into blood plasma
Only Liver responds as only they have cells that have receptors binding to glucagon
Liver cells activate enzyme that converts glycogen to glucose. They also increase gluconeogenesis - conversion of amino acids and glycerol into glucose
Definition of Nervous System
Made up of complex network of cells called neurones
What is a Neurone?
Specialised cell adapted to carrying electrochemical changes called nerve impulses from one part of the body to another
What is a Nerve impulse?
Temporary reversal of the electrical potential across the axon membrane
Reversal is between two states called resting potential and action potential
This is achieved by movement of sodium and potassium ions across membrane
Describe Resting Potential
Inside of Axon negatively charged compared to outside
Resting Potential usually at -70mV
Membrane is polarised
Difference in charge between the inside and outside is achieved by several mechanisms
Describe the Sodium Potassium Pump
Sodium potassium pump actively transports 3 Na+ ions OUT of Axon
For every 3 Na+ transported out, 2K+ pumped INTO the Axon
Describe Action Potential
Inside of Axon is now positively charged compared to outside
Action potential usually around +40mV
Membrane is Depolarised
Reversal of charges caused by energy from a stimulus
Describe stages of an Action Potenial
- Resting Potential - Na+/K+ Pump
- Depolarisation - Voltage-gated Na+ Channel
- Repolarisation - Voltage-gated K+ Channel
- Resting Potential - Na+/K+ Pump
How does an Action Potential occur?
Voltage-dependent Na+ channels open. Na+ flow into the axon, depolarising the membrane
Voltage-dependent Na+ channels close. Voltage-dependent K+ channels open. K+ leave the axon, repolarising the membrane
The membrane is hyperpolarised. Voltage-dependent K+ channels close. K+ diffuse back into the axon to recreate the resting potential
Describe stages of Unidirectional Nerve Impulse Progression
Action Potential (Pre-synaptic “sending” cell)
Synapse
Post-synaptic (“Receiving” cell)
What is Cell Body?
Contains nucleus & Endoplasmic Reticulum. Production of proteins and neurotransmitters
What are Dendrons?
Small extensions of cell body. These sub-divide into smaller branched fibres called Dendrites. These carry nerve impulses towards cell body
What are Axons?
Single long fibre that carries impulse away from cell body
What are Schwann Cells (in PNS)?
Surround axon to protect it and provide electrical insulation. They also carry out phagocytosis and contribute to nerve regeneration
What are Oligodendrocytes?
Produce Myelin in the CNS
What is Myelin Sheath?
Covering around axon. Formed from membranes of Schwann cells or oligodendrocytes. Rich in Myelin, transmit nerve impulses faster. Insulates neurone.
What are Nodes of Ranvier?
Gaps between adjacent
Define Hormonal System
The hormonal system is made up of glands and hormones and it sends information as chemical signals
Hypothalamus & Pituitary
- Together these regulate many endocrine cells and glands in the body
- Pituitary gland has 2 major lobes
> Posterior pituitary (contains neurosecretory nerve endings from hypothalamus)
> Anterior Pituitary (nonneural endocrine cells)
Thyroid & Parathyroid Glands
- Hormones from the thyroid gland are vital to normal development and metabolism
- Parathyroid hormone helps regulate calcium levels in the blood
Thyroid Gland
- Located in front of trachea
- Main Secretions make up thyroid hormone
How do Thyroid Hormones affect Metabolism, Growth & Development
- Simple Goiter
- Hypothyroidism
- Hyperthyroidism
State facts about Parathyroid Glands
- Four on the back of thyroid gland
- Produce PTH which is main regulator of calcium blood levels
RICKETS:
- Vitamin D deficiency; little calcium absorbed; skeletal abnormalities
HYPERPARATHYROIDISM:
- Increased PTH in blood.
Symptoms: high blood Ca levels and kidney stones. Can lead to osteoporosis.
State facts about Adrenal Glands
- On top of each kidney
- Divided into 2 sections
1. Adrenal Cortex
2. Adrenal Medulla
State facts about the Pineal Gland
- In the brain
- Produces melatonin
- Influences sleep/wake cycles
- Biological Clock
- SAD (Seasonal Affective Disorder)
What are the different blood vessels?
Artery, Veins, Capillaries
Describe the Artery
- Thick outer wall
- Small Lumen
- Thick layer of muscles and elastic fibres
Describe the Vein
- Thin layer of muscle and elastic fibres
- Large lumen
- Fairly thin outer wall
Describe Capillary
- Very small lumen
- Wall made of single layer of cell
