UNIT THREE BIOLOGY AREA OF STUDY #2: DETECTING & RESPONDING EXAM REVISION LECTURE CHP 6: COORDINATION & REGULATION NERVOUS SYSTEM

UNIT THREE

BIOLOGYAREA OF STUDY #2: DETECTING & RESPONDING

EXAM REVISION LECTURE

CHP 6: COORDINATION & REGULATIONNERVOUS SYSTEM

CHP 6 TOPIC 1: THE NERVOUS SYSTEM

The nervous system is divided into two parts; the Central Nervous System (CNS) and the Peripheral Nervous System (PNS)


NERVOUS SYSTEM

Peripheral Central

Somatic Autonomic Brain Spinal Chord

Sensory Motor

Sympathetic Parasympathetic

Central Nervous System Peripheral Nervous System

CHP 6 TOPIC 1: THE NERVOUS SYSTEMDIVISION FUNCTION COMPONENTS

CNS

Receives impulses from sensory nerves, coordinates responses and directs the action of effectors.

Brain: coordinates actions and responses, both voluntary and involuntarySpinal Cord: carries messages from the brain to motor and autonomic nerves, and to the brain from sensory nerves. Directs responses in a reflex arc.

PNSSomatic

Contains nerves (sensory/ afferent) which carry messages from receptors to the CNS, and from the CNS to voluntary muscles (motor/ efferent)

Sensory(Afferent): carries messages from external receptors to the CNS Visceral (afferent): carries messages from internal receptors to the CNS

Motor/ Efferent: carries messages from the CNS to skeletal muscles (voluntary responses)

PNSAutonomic

Contains nerves involved in involuntary responses such as churning and peristalsis in the gut, secretions of glands, heart rate changes and pupil dilation and constriction

Sympathetic: generally heightens activity of internal systems, prepares the body for actionParasympathetic: generally lessens activity of internal organs, returns the body to a resting state

• “ Fight or flight” response

• Release adrenaline and noradrenaline

• Increases heart rate and blood pressure

• Increases blood flow to skeletal muscles

• Inhibits digestive functions

CENTRAL NERVOUS SYSTEMBrain

Spinalcord

Dilates pupil

Stimulates salivation

Relaxes bronchi

Accelerates heartbeat

Inhibits activity

Stimulates glucose

Secretion of adrenaline,nonadrenaline

Relaxes bladder

Stimulates ejaculationin male

Sympatheticganglia

Salivaryglands

Lungs

Heart

Stomach

Pancreas

Liver

Adrenalgland

Kidney

SYMPATHETIC


• “ Rest and digest ” system

• Calms body to conserve and maintain energy

• Lowers heartbeat, breathing rate, blood pressure

CENTRAL NERVOUS SYSTEMBrain

Spinalcord

Stimulates salivation

Constricts bronchi

Slows heartbeat

Stimulates activity

Contracts bladder

Stimulates erectionof sex organs

Stimulates gallbladder

Gallbladder

Contracts pupil

PARASYMPATHETIC


The Brain

Note: meninges (membranes) surrounding the CNS tissue (not myelin!) and fluid between the tissue and meninges helps to cushion the CNS from knocks


Pineal Gland: regulates some circadian rhythms.

Cerebral Cortex: receives sensory information, links sensory and motor functions

Cerebellum: coordinates posture and balance

Thalamus: relays sensory information from the brainstem midbrain including pons and medulla oblongata ( heart rate and breathing), spinal cord and cerebellum to the cerebral cortex.

Brain Stem: links brain and spinal cord, controls some autonomic functions and reflexes

Hypothalamus: control centre for most homeostatic mechanisms, involuntary nervous and hormonal responses – releases many hormones

Topic CHP 6.1 Questions:1. What does and EEG (electroencephalogram) measure? __________________________2. Name three things that protect the brain and spinal cord from physical shock? _________________________, _______________________, ______________________3. What part of the brain is the control centre for temperature maintenance, water balance and

blood pressure? __________________________________4. True/ False: the thalamus receives impulses from motor neurons and directs them to the

various parts of the brain where they are interpreted?5. The folded surface of the cerebrum (largest part of the brain) is called what? __________________ _________________6. Which part of the nervous system would be involved in the following transmissions:

i. Information from the eye to the CNS via: Somatic or Visceral neuronsii. From the skin: Somatic or Visceral neuronsiii. From the heart: Somatic or Visceral neuronsiv. To the heart to increase heart rate: ________________________v. To the heart to decrease hearts rate: _______________________vi. To the effector muscles of the arm: _________________________vii. To blood vessels to constrict blood flow: ____________________

/ 12 Marks

CHP 6 TOPIC 2: NEURONS

The nervous system of complex animals receives and carries information (stimulus) from receptors, processes (control centre) responses and directs (to effectors) those responses. In order to achieve these functions the nervous system contains many types of specialised cells, known as neurons.

CHP 6 TOPIC 2 NEURONS

Dendrites

Cell Body

Axon


Neurons:• Specialised cells which make up the nervous system are called neurons

• a typical neuron has:• dendrites: highly branched extensions of the cell body that receive and then carry

information towards the cell body• a nucleus within the cell body • an axon: an extension that carries information away the cell body to the axon terminals

(transmit chemical messages to other neurons or effectors)

• the presence of the myelin sheath, lipid protein based (on affector and effector neurons) increases the rate at which a nerve impulse is conducted along the axon. Myelin sheath is composed of Schwann cells wrapped around the axon.

• Three types of neurons:• sensory (affector) neurons: (PNS -cell body roughly central on the axon)• connecting (inter) neurons: (CNS - found in the CNS, contains many connections to

other cells) • motor (effector) neurons: (PNS - cell body is at the site of the dendrites, adjacent to

CNS)

Cells of the nervous system. (a) A typical sensory neuron (b) A typical motor neuron (c) Structure of a nerve (d) A typical connector or inter neuron


Myelination

• Schwann Cells– Act as insulators to the nerve– Lipo-protein based– Separated by Nodes of

RanvierNode of Ranvier


http://images.google.com/imgres?imgurl=http://biology.clc.uc.edu/graphics/bio105/schwann.jpg&imgrefurl=http://biology.clc.uc.edu/courses/bio105/nervous.htm&h=150&w=150&sz=10&hl=en&start=12&tbnid=tKwRiAlyhVQqAM:&tbnh=96&tbnw=96&prev=/images?q=schwann+cell&gbv=2&svnum=10&hl=en

Myelination cont• Schwann Cell

– Speed up conduction of impulse

– Depolarization skips from one node to another.


Synapse• Receptor site receives neurotransmitters• Neurotransmitters change permeability of membrane.• Ions flood into membrane setting off a action potential in post-synaptic cell.• Position of neurotransmitter substances (ends of axons) ensures that nerve impulses are

transmitted on one direction only: from an axon to another neuron, muscle or gland.


The Structure of a Synapse.


Reflex Arc

Acts in an “emergency response”Cuts time of response.


Sensory NeuronInterneuronMotor NeuronCreate reflex arc

Reflex Arc



Comparison of reflex arc, voluntary responses and involuntary responses.

Reflex Arc Voluntary Response Involuntary Response

Receptors Involved Generally pain any Any

Transmission to CNS Sensory (afferent) nerves

Sensory (afferent) nerves

Sensory (afferent) nerves

CNS Involved Spinal cord brain Brain-hypothalamus

Transmission from CNS Motor neurons Motor neurons Autonomic nerves

Topic CHP 6.2 Questions:

1. Name the two types of neurons of the PNS: ________________, __________________2. Name a distinctive feature of a sensory neuron that differs from:

i. A connecting/ interneuron: _________________________________________________ii. A motor neuron: __________________________________________________________

3. True/ False: Myelin sheath is made of phospholipids4. True/ False: Neurons are responsible only for electrical impulses and not chemical

messengers5. Name two features of a neuron that would speed up electrical impulses:

i. __________________________________ ii. ______________________________________

6. (Fill in gap) Axon terminals forms_____________ with other neurons or with ___________________

7. Another name for an effector neuron is: ____________________8. A very simple involuntary nervous response such as lifting of the foot from a painful stimulus

is known as a: ___________________ 9. Acetylcholine is an example of ______________________ substance and is found in the

brain and PNS at neuromuscular junctions.10. True/ False: vesicles containing transmitter substances occur only at the ends of axons

/ 10 Marks

Resting Potential

Cells are set up as electrically polarized.– They are in “resting state”– Ready to do work.– A more + charge outside the cell than inside– Created by Na+/K+ pumps

CHP 6 TOPIC 3 NERVE IMPULSES

ACTION POTENTIAL

– These resting neurons are easy to knock off balance

– Electrical, chemical, or mechanical stimulus can move them to an action state.

– Once the “threshold” level is met, signal is sent.





• as an impulse moves along an axon, the permeability of the membrane changes so that positive Sodium ions (Na+) move into the neuron through ion channels

• the change in permeability moves along the neuron

• Sodium ions (NA+) move into the neuron causing a change in polarity (from negative to positive). Potassium ions (K+) move out of the neuron (momentarily). When Na+ and K+ are momentarily together inside the neuron, the charge is positive

• after a nerve impulse has passed along the membrane, the original distribution of ions across the membrane is restored

• the larger the axon’s diameter, the faster the impulse moves along it

• the presence of myelin increases the speed of an impulse (it also insulates one neuron from another!)

• Multiple sclerosis is an example of a disease caused by damaged myelin sheath

• an unstimulated nerve is said to have ‘resting potential’ an activated nerve has ‘action potential’ (the wave being the action potential)


Networks of nerve cells

• neuron pathways are of two kinds: diverging or converging

• diverging pathway: a single axon of one neuron branches and links up wit a larger number of postsynaptic neurons.

• converging pathway: many presynaptic nerves come together to influence a smaller number of synaptic neurons, ultimately one.

• one advantage of the convergence system is that one cell can have multiple signals that influence an outcome.

• In a multi pathway system of signaling messages, some may be excitatory and others may be inhibitory. It is the balance between excitatory and others may be inhibitory that determines the kind of signal or whether a target cell receives any signal



1. True/ False: In a ‘resting state’ Na+ ions are in greater concentration outside the neuron than inside

2. In a ‘resting state’, the outside of the neuron is: positively/ negatively charged 3. Name two things that can stimulate a dendrite of an afferent neurone:

__________________, & __________________________4. Name two things that neurotransmitter can do to a target cell: __________________ &

_______________________5. True/ False: the smallest amount of neurotransmitter substance is enough to start an action

potential6. True/ False: Na+ and K+ dissolve through the lipid bilayer passively7. In less than ten words, what is meant by membrane depolarisation: ____________________

___________________________________________________________________________8. What is the charge of a ‘resting cell’: +70 millivolts/ -70 millivolts 9. Name one disease caused by ineffective myelin: ________________

/ 9 Marks

• signal transduction is the process by which a cell converts one kind of signal into another by a series of relay molecules

• signals initiating transduction include:• hormones• neurotransmitters• neurohormones• environmental stimuli (i.e. light- photosynthesis!)

• cellular responses to transduction include:• activation of a gene- protein production• alteration of cellular activity, such as

• increased cellular secretions• Changes in cell permeability• Increased rates of chemical reactions

CHP 6 TOPIC 4 SIGNAL TRANSDUCTION

Across A Synapse


Principles of cell communication



neurotransmitters (being protein-based) cannot pass through the plasma membrane; they interact with a receptor on the cell surface.


Fatty-acid-derived hormones pass through the plasma membrane and combine with a cytoplasmic receptor, which then passes into the nucleus where they directly activate or suppress particular genes.


Neurohormones• are chemicals released directly into the blood

• travel to a target organ where the signal is transduced and the receptor cells respond

• neurons in the hypothalamus of the brain has several different neurohormones. These are released into the blood and travel to the pituitary cells, both anterior and posterior, where they exert their effect

Examples: thyrotropin-releasing hormone (TRH) signals anterior pituitary cells to producethyroid stimulating hormone (TSH);

This is an example of the nervous and endocrine systems interacting together

Other examples: thyroptropin releasing hormone (TRH); thyroid stimulating hormone (TSH); corticotropin releasing hormone (CRH)




1. Pituitary cells, both anterior and posterior are target cells for a number of different neurohormones. Name one neurohomrone that targets the pituitary and identify where it is produced (source): Name: ___________________ Source: ________________________ (2 marks)

2. Define signal transduction: __________________________________________________ _________________________________________________________ ________________

3. What is a hormone?4. List three possible cellular responses to signal transduction:____________________________,

____________________________, ____________________________ 5. What kind of cells produce neurohormones? _____________________________________6. What kind of cells are the target of: (1 mark each)

i. neurohormones: ________________________________ii. Neurotransmitters: ______________________________iii. Insulin: ________________________________________iv. Glucagon: ______________________________________v. Interleukin-1: ___________________________________

7. List three types of substances that are transduced: __________________, _____________, _____________________________

8. True/ False: all messengers pass through target cell membranes to induce a response from the target cell9. True/ False: motor neuron axon terminals never touch another neuron but can physically connect with muscles

and glands10. Neurotransmitter substances move faster/ slower than electrical impulses and quickly/ slowly digested by

enzymes of the body11. What term is used to describe the amount of neurotransmitter substance that is enough to result in an

electrical charge from a postsynaptic dendrite: _______________________

/14 Marks

• Paracrine glands

• Endocrine glands

• Exocrine glands

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UNIT THREE BIOLOGY AREA OF STUDY #2: DETECTING & RESPONDING EXAM REVISION LECTURE CHP 6: COORDINATION & REGULATION NERVOUS SYSTEM