Chapter 3- The Nervous System's Functional Units , Chapter 2- What is the nervous systems functional anatomy, Chapter 1- What are the origins of brain and behaviour?

what are the nervous system's functional units?

1. Cells of the nervous system

2. Internal structure of a cell

3. Genes, cells and behaviour

Golgi's view on the internal structure of the cell

nervous system is composed of a network of interconnected fibers: a 'nerve net'

Cajal's view on the internal structure of the cell

- Nervous system is made of discrete cells

- Neuron hypothesis: Neurons are the units of brain function

Dystonia

- Disorder in which muscles contract involuntarily, causing repetitive or twisting movements

- Rare, dopa-response condition, stems from dopamine deficiency

- Beery twins successful treatment

Cajal's Neuron Theory

Neurons are the nervous system's functional units; now the accepted theory of brain organisation

Basic Structure of Neuron

- Core region called the cell body or soma

- Branching extensions or dendrites collect info from other cells

- Main root is the single axon, which carries messages to other neurons

- A neuron has only one axon, but most have many dendrites

Soma

core region of the neuron. also called the cell body

Dendrites

Branching extensions of the neuron that collect info from other cells

axon

main root of the neuron that carries messages to other neurons (only one)

Role of neurons

- Acquire info, store it as memory, interpret it and pass it along to other neurons to produce behaviour.

- In doing so, they regulate body processes such as breathing, heartbeat and body temp

- Also regulate cognitive processes incl learning, decision making and thought

Subdivisions of neurons

- Dendrites

- Cell body/soma

- Axon

Dendritic spines

protrusion from a dendrite that greatly increases its surface area and is the usual point of contact with axons or other cells

Axon hillock

Juncture of the soma and axon, where the action potential begins

Axon collaterals

Branches of an axon

Telodendria

End branches of an axon

Terminal button

Knob at the tip of an axon that conveys info to other neurons;also called an end foot

Synapse

- Gap between one neuron and another

- Usually between an end foot of the axon of one neuron and a dendritic spine of another neuron

3 functions of neurons

1. Sensory neurons

2. Interneurons

3. Motor neurons

Sensory neurons

Carry info from the sensory receptors in or on the body to the spinal cord

Interneurons

Include associate sensory and motor activity within the central nervous system

Motor neurons

-Send signals from brain to spinal cord to muscles

-Reside in lower brainstem and spinal cord

- have extensive dendritic networks, large cell bodies and long axons that connect to muscles

-All efferent (outgoing) neural info must pass through motor neurons to reach the muscles

Types of sensory neurons

Bipolar and somatosensory

Bipolar neuron

- Contains one axon and one dendrite

- transmits afferent (incoming) sensory info from the body to the spinal cord

Types of interneurons (association cells)

1. Stellate cell

2. Pyramidal cell

3. Purkinje cell

Stellate cell

small, many dendrites extend around the cell body; larger brains contain more (behavioural complexity)

Pyramidal cell

- Has long axon

- Pyramid shaped cell body

- 2 sets of dendrites- apical and basal

- Carries info from cortex to rest of brain and spinal cord

Purkinje Cell

- Has extremely branched dendrites that form a fan

- Carries info from cerebellum to rest of brain and spinal cord

Organisational aspects of neurons

Input, association and output

Glial cell

- Provides insulation, nutrients, and support and that aids in repairing neurons and eliminating waste products

- Is produced throughout an organism's life, and errors in their replication are a main source of abnormal growths (brain tumours)

Classes of glial cells

1. Ependymal cell

2. astrocyte

3. Microglial cell

4. Oligondendrogial cell

5. Schwann Cell

Tumor

- Mass of new tissue that grows in an uncontrolled manner independent of the surrounding structures

- In adults: glial or other supporting cells

- In infants: developing neurons

Major types of tumor

1. Gliomas

2. Meningiomas

3. Metastatic tumors

Ependymal cells

- Small, ovoid, found in the walls of the ventricles

- Make and secrete cerebrospinal fluid (CSF)

Hydrocephalus

Buildup of pressure in the brain and swelling of the head caused if the flow of CSF is blocked. Can result in severe intellectual impairment

Functions of Astrocytes

- Provide structural support for neurons

-Transport substances between neurons and capillaries (blood-brain barrier)

- Enhance brain activity by providing fuel to active brain regions

- Promote healing of damaged brain tissue

Tripartite Synaptsomics

- Newest area of research into astrocyte function

- Focus on the role they play in neuron to neuron communication and role of many synaptic connections

Blood-brain barrier

Astrocyte processes attach to neurons and to blood vessel cells, stimulating them to form tight junctions ansd so form the blood-brain barrier

Microglia

- Originate in the blood as offshoot of immune system

- Involved in scavenging of debris (dead cells)

- Monitor the health of brain tissue and play the role of its immune system

- Identify and attack foreign tissue

- invade the area to provide growth factors that aid in repair when brain cells are damaged

Myelin

Glial coating that surrounds axons in the central and peripheral nervous systems; prevents adjacent neurons from short-circuiting

Oligodendroglia cells

Glial cells in the central nervous system that myelinate axons

Schwann cells

Glial cells in the peripheral nervous system that myelinate axons

Glial cells, disease and neuron repair

- MS: nervous system disorder associated with loss of myelin; damage to oligodendroglia

- Peripheral nervous system: microglia anf schwann cells help repair neurons

- Central nervous system: repair doesn't take place; regrowth may be inhibited

Neuron Repair Process

1. When a pripheral axon is cut, the axon dies.

2. Schwann cells first shrink and then divide, forming glial cells along the axon's former path.

3. The neuron sends out axon sprouts, one of which finds the Schwann-cell path and becomes and becomes a new axon

4. Schwann cells envelop the new axon, forming new myelin.

The 2 classes of nervous system cells are ____

a.glia and dendrites

b.axons and neurons

c.neurons and glia

d.axons and dendrites

c.

A cell that carries efferent information from the brain and spinal cord to make muscles contract is called a(n) _____.

a.interneuron

b.pyramidal cell

c.Purkinje cell

d.motor neuron

d.

Each neuron has _____ axon(s) to carry messages to other neurons.

a.five

b.eight

c.two

d.one

d.

Internal structure of a cell

- To a large extent, a cell's proteins determine its characteristics and functions

- Each cell can manufacture thousands of proteins

- Water, salts and ions play prominent parts in the cell's functions

Molecule

-The smallest unit of a protein or any other chemical substance

-Formed when atoms bind together

element

a substance that cannot be broken down into another substance

Atom

Smallest quantity of an element that retains the properties of that element

Cell membrane

Membrane surrounding the cell.

Separates intracellular and extracellular fluid.

regulates movement of substances into and out of the cell.

Made up of phospholipids

Intracellular fluid

fluid in which the cell's internal structures are suspended

Nuclear membrane

membrane surrounding the nucleus

Endoplasmic reticulum

Folded layers of membrane where proteins are assembled

Golgi body

Membranous structure that packages protein molecules for transport

Tubule

tiny tube that transports molecules and helps give the cell its shape

Microfillaments

threads involved in movement of cytoplasm

Mitochondrion

Structure that gathers, stores and releases energy

Lysosomes

sacs containing enzymes that break down wastes

Gene

- Segment of DNA that encodes the synthesis of particular proteins.

-Sequence of nucleotides determines which amino acids are to be joined from the particular protein

Chromosome

- Double Helix structure that holds an organism's entire DNA sequence

- Contains the genes

Protein Synthesis

1. DNA uncoils to expose a gene, a sequence of nucleotide bases that encodes a protein.

2. One strand of the gene serves as a template for transcribing a molecule of mRNA.

3. The mRNA leaves the nucleus and comes in contact with ribosomes in the endoplasmic reticulum.

4. As a ribosome moves along the mRNA, it translates the bases into a specific amino acid chain, which forms the protein.

Ribosomes

Protein structures that act as catalysts for protein synthesis

Translation

-Later phase of protein synthesis in which the messanger RNA travels from nucleus to the ER

-mRNA is translated into a particular sequence of amino acids to form a protein

Transcription (making a copy)

Early phase of protein synthesis in which the DNA strands unwind and a complementary strand of mRNA (ribonucleic) is produced

Codon

Sequence of three bases on mRNA that codes for a particular amino acid

Amino acid

-Consists of a central carbon (C) atom bound to a hydrogen (H) atom, an amino group, a carboxyl group, and a side chain (R).

-Linked together by a peptide bond.

-Polypeptide chain: a series of amino acids

Enzyme

Protein catalyst that facilitates the cell's chemical reactions

Golgi Bodies

Package proteins in membranes (vesicles) and give them a label indicating where they are to go.

Microtubules

Transport the vesicles to their destination inside or outside the cell

Channel

Opening in a protein embedded in the cellmembrane that allows the passage of ions

Gate

Protein embedded in a cell membrane that allows substances to pass only when open

Pump

Protein embedded in a cell membrane that actively transports a substance across the membrane

Which of these is not one of the constituent parts of a cell?

a.nucleus

b.lysosome

c.basal ganglia

d.mitochondrion

c.

The _____ is an extension of the nuclear membrane.

a.extracellular fluid

b.endoplasmic reticulum

c.Golgi body

d.tubule

b.

Genotype

Genetic makeup

Phenotype

Physical and behavioural traits

Mendelian Genetics

Studies how genes influence our traits

Allele

A cell contains 2 copies of every gene, one inherited from mother and one from father. Matching copies are alleles

Dominant Allele

The member of the gene pair that is routinely expressed

Recessive allele

the member of the gene pair that is routinely unexpressed

Homozygous

Having 2 identical alleles for a trait. The two encode exactly the same protein

Heterozygous

Having 2 different alleles for the same trait. they encode proteins that can produce 3 possible outcomes:

Only mother's allele expressed; only father's allele expressed; both alleles expressed simultaneously

Mutations

Involve errors in nucleotide sequence when reproductive cells make gene copies

Acquired mutations

- Not heritable

- Have potential to affect behaviour

- May be due to mitotic errors

Allele disorders that affect the brain

- Tay-Sachs disease

- Huntington disease

Tay-Sachs disease

- Inherited birth defect caused by loss of genes that encode the enzyme necessary for breaking down certain fatty substances.

- Appears 4-6 months after birth; results in intellectual disability, physical changes, and death by age 5

- Caused by a recessive allele

Huntington disease

- Autosomal disorder that results in motor and cognitive disturbances

- Caused by an increase in the number of CAG repeats on chromosome 4

- The buildup of an abnormal version of the huntington protein kills brain cells, esp basal ganglia and the cortex

- Characterised by memory impairement and mared changes in personality, leading to nearly total loss of healthy behavioural, emotional and intellectual functioning

Genetic disorders

result from aberration in part or all of a chromosome rather than a single defective allele

Down syndrome

•Chromosomal abnormality resulting in intellectual impairment and other abnormalities, usually caused by an extra copy of chromosome 21 (trisomy).

•One parent (usually the mother) passes on to the child two copies of chromosome 21 rather than the normal single chromosome.

Genetic engineering approaches

- Selective breeding

- Cloning

- Transgenic techniques

- Knockouts

Cloning

- Produces an offspring that is genetically identical to another animal

- Used to preserve valuable traits, studying relative influences of hereditary and environment, or producing new tissue or organs for transplant to the donor

Gene modification

Modifying genes by altering its code (base pairs)

How can epigenetic mechanisms influence protein production?

1. By blocking a gene so that it cannot be transcribed

2. By unlocking a gene so that it can be transcribed

Histone modification

DNA may unwrap or be stopped from unwrapping from the histone

Gene (DNA) methylation

transcription of DNA into mRNA may be enabled or blocked

mRNA modification

mRNA translation may be enabled or blocked

Reprogramming

Allows the cells of the fetus to essentially start afresh and make their own genetic and epigenetic future

Transgenerational epigenetic inheritance

Shows that some life experience of ancestors can be inherited in their offspring, at least for a few generations

If a pair of alleles are identical they are ___?

a.dominant

b.recessive

c.homozygous

d.heterozygous

c.