Biology 2024

Receptor

specialised cell that can detect changes in an organism's environment.
(the change = the stimulus)

Temperature receptors

respond to changes in temperature. (touch)

Photoreceptors

respond to light energy (sight)

Mechanoreceptors

respond to mechanical stimuli such as touch, pressure or vibrations. (touch)

Sound receptors

respond to vibrations (sound)

Chemoreceptors

respond to specific chemicals (smell and taste)

effector examples

glands and muscles

Effector

cause a response to the stimulus (muscles contract, glands release hormones)

types of nervous action

Voluntary actions

The decision starts in the brain that coordinates a response in many different parts of the body.

Involuntary actions

Processes constantly occurring in our bodies

We cannot make these things happen, and cannot choose to we stop them.

Some activities, such as breathing and blinking are partly voluntary and partly involuntary: we breathe automatically without thinking about it, and yet we can alter the rate of our breathing if we want to.

reflex arc

The nervous system communicates information via a stimulus-response model:

Stimuli (internal or external) are converted into electrical signals by receptors

Effectors (muscles or glands) convert the electrical signals into a response

describe the process of a reflex arc

What carries the electrical signals around your nervous system?

NEURONES

How does a signal travel across a neuron?

Dendrites pick up electrical signals from other neurons nearby. (nerve signals)

Myelin insulates the nerve fibres, so they carry the impulses much faster.

The nerve signal passes to the cell body, then along the axon, where it might be passed onto another neuron/effector.

types of nerve cells

sensory neurons, motor neurons, interneurons

sensory neurons

pick up an impulse from a receptor cell and carry it to the spinal cord

Relay neuron

picks up impulse from the sensory neuron then relays it to other neurons. Pass the impulse to the brain or to a motor neuron.

Motor neurons

pass the impulse to an effector

draw and label a neuron diagram

Sensitivity

ability to detect and process information

The sensitivity homunculus

concept in neuroscience

represents the sensory distribution of the body on the cerebral cortex (brain)

way to visualize how different parts of the body are mapped in the brain

Neurotransmitters

Dopamine
Adrenaline
Noradrenaline
Serotonin
GABA
Acetylcholine
Endorphins

Excitatory

“excite” the neuron and cause it to “fire off the message,” → the message continues to be passed along to the next cell. E.g. glutamate, epinephrine and norepinephrine

Inhibitory

block or prevent the chemical message from being passed along any farther

Modulatory

influence the effects of other chemical messengers. They “tweak” or adjust how cells communicate at the synapse. They also affect a larger number of neurons at the same time. E.g. dopamine

What is a synapse?

A synapse is a junction between two neurons across which messages pass.

form of messages
1)across neurons
2)between

1)electrical
2)chemical

draw a synapse

basic format of a reflex arc

stimulus → receptors → sensory neuron → relay neuron → motor neuron → effector → response

synaptic vesicle

storage site for neurotransmitters

synaptic clef

a gap into which neurotransmitters are released from the axon terminal

Nervous system

The main job of the nervous system is to transmit messages from one part of the body to another.

Nerve impulses are tiny pulses of electricity which travel rapidly through the CNS and along the nerves.

CNS vs PNS

glands

type of effector that produces chemicals such as hormones as a response

muscles

type of effector that causes movement (most of the time) as a response

Reflexes

Reflexes are automatic responses that do not need the involvement of the brain and are a lot faster because of it.

Receptor

specialised cell that can detect changes in an organism's environment.
(the change = the stimulus)

Axon

portion of a nerve cell that carries nerve impulses away from the cell body

cell body

Largest part of a typical neuron; contains the nucleus and much of the cytoplasm

central nevous system

consists of the brain and spinal cord

coordinator

controls and coordinates all involuntary and voluntary functions of the body

Dendrite

branching extensions of a neuron that receive messages and conduct impulses toward the cell body

Effector

An organ (a gland or muscle) that becomes active in response to nerve impulses. (stimulus)

Interneuron

neurons that internally communicate between the sensory inputs and motor neurons

involuntary response

A response to a stimulus that occurs without someone making a conscious choice. They are automatic, such as reflexes.

motor neurons

neurons that carry signals from the spinal cord to the muscles to produce movement and all voluntary responses, such as speaking and breathing.

myelin sheath

insulating layer around nerves, made of proteins and fatty substances

Neurotrasmitters

chemical found in the synaptic vesicles that, when released, has an effect on the next cell

peripheral nervous system

the sensory and motor neurons that connect the central nervous system to the rest of the body

receptor

protein that detects a signal molecule and performs an action in response

reflex arc

the nerve pathway involved in a reflex action including at its simplest a sensory nerve and a motor nerve with a synapse between.

response

a reaction to a stimulus

senses

systems we have throughout our bodies that allow us to detect information and transform energy into neural impulses

sensory neurons

neurons that carry incoming information from the sensory receptors to the brain and spinal cord

Stimulus

any event or situation that evokes a response

Synapse

A junction where information is transmitted from one neuron to the next.

Variation

differences between individuals of the same species.

Genetic Variation

Differences caused because individuals have different genotypes
→ slight differences in certain genes in the chromosomes.

Where is DNA stored?

chromosomes

How many chromosomes do humans have?

46 (23 pairs)

Environmental Variation

Variation caused by an individual's surroundings (environment).

Characteristics of animal and plant species can be affected by factors such as climate, diet, accidents, culture and lifestyle.

Discontinuous variation

inheritance pattern in which traits are distinct and are transmitted independently of one another

Always caused by genes.

Examples: natural hair colour, blood groups, free/attached earlobes

Continuous Variation

Gradual variation

Generally caused by genes and the environment.

E.g. mass, leaf length, height, skin colour.

Inheritance

the transmission of genetic information from generation to generation.

DNA

the molecular blueprint for inheritance

DNA is the universal genetic code!

ALL organisms have DNA made up of the same structure.

What is the only difference between species or individuals of the same species, regarding their DNA?

the sequence (order) of the nitrogen bases. – The A, T, C and G’s are just arranged differently.

why aren't fruits of the same plant identical?

they are fertilised by different plants

A segment of DNA is called ....

a gene

genes

DNA segments that serve as the key functional units in hereditary transmission. Each gene controls a trait.

How do we inherit traits?

Humans have 46 chromosomes (23 pairs) in each body cell.

Half from each parent – carried in the sperm and egg. So, sex cells only carry 23 chromosomes.

The 1st 22 pairs do NOT determine your sex – they carry genes for other traits.

The 23rd pair are the sex chromosomes

XX = female, XY = male

male chromosomes

XY - If the 23rd pair of chromosomes are the different sizes, XY, then the organism is a male.

Female chromosomes

XX - If the 23rd pair of chromosomes are the same size, XX, then the organism is a female.

autosomes

Chromosomes that are not directly involved in determining the sex of an individual.

Organise these structures in order of size (smallest → largest):

Cell

DNA

Chromosome

Nucleus

DNA
Chromosome
Nucleus
Cell

nucleotide

A building block of DNA, consisting of a five-carbon sugar covalently bonded to a nitrogenous base and a phosphate group.

DNA is made of ...

nucleotides

DNA structure

Along the backbone of the structure is a Phosphate molecule bonded to a sugar called Deoxyribose.

There are two lines of phosphate-sugars like a ladder called a double helix. Connecting the two lines of the ladder together are bases.

Bases of DNA

There are four bases Adenine, Thymine, Cytosine and Guanine

complementary base pairs

A (Adenine) will always form weak hydrogen bonds with T (Thymine)

G (Guanine) will always form weak bonds with C (Cytosine)

Where is DNA found in eukaryotes?

nucleus

Where is DNA found in prokaryotes?

cytoplasm

DNA is an abbreviation for

deoxyribonucleic acid

3 parts to a nucleotide

Deoxyribose sugar (5 carbons - pentagon shaped)

Phosphate group

Nitrogen base

Draw a Nucleotide Structure

Mutation

a change in a gene or chromosome.

A change in a gene creates new alleles.

alleles

Alleles are all the different versions of the same gene.

Once scientists have the genome of an organism they can ....

→ figure out what the bases code for

→ then, it is possible to edit its genetic information.

Genetic Modification

Changing the genetic material of an organism by removing, changing or inserting genes.
- This can include inserting a gene from one species into an entirely different species.

Recombinant DNA - Using bacteria to produce insulin

sugar phosphate bonding

Allele

An alternative form of a gene.

amino acids

building blocks of proteins

Chromosomes

threadlike structures made of DNA molecules that contain the genes

complementary base pairs

the standard arrangement of bases in nucleotides in relation to their opposite pairing, such as cytosine paired with guanine and adenine with thymine.

DNA

A complex molecule containing the genetic information that makes up the chromosomes.

DNA profile

A distinctive pattern of DNA fragments that can be used to identify individuals

DNA double helix

twisted ladder shape of DNA

Gene

A segment of DNA on a chromosome that codes for a specific trait

genetically modified organisms

An organism whose genetic material has been altered through some genetic engineering technology or technique.