Biology 30

Morinville Community High School

Unit 1: Nervous System

Name: ______________

2

Chapter 11 text p. 364-403 Introduction

Organization of the nervous system Key Concept A: Neurons conduct nerve impulses A1. Structure of a neuron A2. The Nerve Impulse a) a neuron at rest b) How a neuron becomes polarized c) How a nerve signal travels d) How a stronger stimulus is felt e) The speed of nerve impulse transmission A3. Crossing synapses A4. Neurotransmitter chemicals Key Concept B: The nervous system links stimulus to response B1. Impulse transmission pathway B2. Reflex arc Lab: Reflex responses Lab: Visual Reaction Time Key Concept C: The CNS (Central Nervous System) integrates information C1. The spinal cord

function structure

C2. The brain function and structure of:

o cerebellum o pons o medulla oblongata o hypothalamus o cerebrum

cerebral cortex lobes

Key Concept D: The autonomic nervous system • Sympathetic system • Parasympathetic system

Chapter 12 text p. 406-433 Key Concept E: Sensory receptors and sensations

definitions types of sensory receptors

Key Concept F: Sense organs link the environment to the nervous system F1. photoreception: sense of vision Lab: Eye dissection F2. mechanoreception:

sense of sound and balance sense of body position sense of touch/pressure/pain

F3. thermoreception: sense of heat and cold F4. chemoreception

sense of taste sense of smell

Nervous System Unit Outline

NERVOUS SYSTEM UNIT EXAM

3

Organization of the Nervous System

4

A1. Structure of a Neuron text p. 372 cell body: dendrites: axon: axon terminals: The end of the axon forms clumps of knobbed branches called axon terminals myelin sheath: Schwann cell: nodes of Ranvier: uninsulated gaps along the axon

A Motor Neuron

Vocabulary

Key Concept A: Neurons conduct nerve impulses text p. 372-377

5

A2. The Nerve Impulse text p. 372 - 377 membrane potential: resting potential: polarization: a) A Neuron at Rest: not yet transmitting a signal

• The voltage across the plasma membrane is ~ -70 mV

• The minus sign indicates that the inside is negative relative to the outside

• A neuron that exhibits a resting potential is said to be polarized

b) How a neuron becomes polarized The unequal distribution of ions in a polarized membrane is maintained by:

• More K+ leak out by diffusion because there are more ion channels in the membrane; fewer Na+ channels, therefore few Na+ leak in

• Sodium/potassium pumps actively transport three Na+ out for every two K+ pumped in (ATP is the energy source for the ion pumps)

Net effect is that the ECF becomes more positive to the cell's cytoplasm

Vocabulary

A Neuron with a Resting Membrane Potential of -70mV

6

c. How A Nerve Signal Travels

• If a neuron is stimulated (example: a pinch), an action potential occurs: the start of transmitting a nerve signal

• Voltage-gated ion channels open in the following sequence:

1. Resting Membrane Potential

2. Depolarization

3. Repolarization:

4. Hyperpolarization:

5. Return to Resting Membrane Potential

Neuron Action Potential

7

text p. 376 - 378

Refractory period: All –or–none principle: Saltatory conduction: Multiple sclerosis: d) How a stronger stimulus is felt

• A stronger stimulus will NOT generate a larger action potential

• As a stimulus becomes stronger: • frequency of action potentials increases • more neurons fire simultaneously

e) The speed of nerve impulse transmission : • Increases when myelin sheath acts as an insulator (no

myelin sheath --> slower conduction)

Vocabulary

Action Potential Propagation

8

A3. Crossing Synapses text p. 378-380 synapse: neurotransmitters: The mechanism of synaptic transmission 1. Action potential arrives at presynaptic neuron 2. Calcium ions diffuse into the axon terminal 3. Vesicles containing neurotransmitter chemicals fuse with plasma membrane and release neurotransmitter 4. Neurotransmitter diffuses across the synaptic gap from the presynaptic neuron to the post synaptic neuron 5. Neurotransmitter binds with a receptor protein on the postsynaptic neuron membrane 6. This binding results in an ion channel opening and sodium ion diffusing through this channel. This initiates an action potential to begin moving down the postsynaptic neuron because it is depolarized 7. Neurotransmitter is degraded (broken into fragments) by specific enzymes and is released from the receptor protein. 8. Neurotransmitter fragments diffuse back across the synaptic gap to be reassembled in the presynaptic neuron terminal 'buttons'

Diagram of a synapse

Vocabulary

9

Neuromuscular Junctions text p. 380 - 382 neuromuscular junction; Acetylcholine: Cholinesterase:

Vocabulary

10

A4. Neurotransmitter Chemicals text p. 379-382

• Have either excitatory or inhibitory effects on the postsynaptic membrane: depends on what type of ion channels are opened by receptors on the postsynaptic neuron .

Excitatory neurotransmitters: text p. 379 Inhibitory neurotransmitters: text p. 380

Examining nerve cells in salamanders revealed the following information: The resting potential of the nerve cells is -80mV.

Each neuron has a threshold potential unique to that particular cell.

If an action potential is generated, the membrane potential depolarizes a total of 110 mV.

The time duration of an action potential in a localized area is approximately 2.0 ms.

1. Sketch a graph of this action potential, including the values for time and membrane potential on the correct axes.

Check your Understanding!

11

Through experimentation it is found that neuron P

synapses with neurons Q and R and that neuron P is excitatory. When a single above-threshold stimulation is applied to the neuron, an action potential is generated. This will cause enough transmitter substance to be released at each synapse so that a postsynaptic depolarization of 15mV occurs. The threshold potential of postsynaptic neuron Q is 13 mV above resting and the threshold potential of postsynaptic neuron R is 18 mV above resting. (Reminder: An action potential is formed as the membrane depolarization is raised above the threshold.) A single, above-threshold stimulus is applied to Neuron P. A voltmeter is used to record the changes in membrane potential of neurons Q and R. 2. Draw a stick diagram of these three neurons 3. Does depolarization occur in Q? Give a reason for your answer. 4. Does depolarization occur in R? Give a reason for your answer.

5. Of neurons Q + R, which one(s) will exhibit an action potential? Explain the difference between depolarization and an action potential 6. Suppose that in each of the neurons ( P,Q, and R) action potentials are achieved. Which ion gated channels open just prior to the action potentials? Which ion gated channels open after an action potential as been ahieved? Neurotransmitters and Their Functions Neurotransmitter Function Effects of abnormal

production is linked to sensations of

pleasure (reward center of the brain), such as eating

inadequate production linked to Parkinson's disease

is involved in mood control

inadequate amounts in the brain synapses linked to depression

acts as a natural pain killer in the brain; also affects emotional areas of the brain

deficiency linked to an increased risk of alcoholism

complements epinephrine (adrenalin) which readies the body in an emergency situation

overproduction linked to high blood pressure

Vocabulary

12

B1. Impulse transmission pathway neuron: nerve: Three functions of neurons in your body: SENSORY INPUT: 1. Sensory Receptors:

2. sensory neurons: INTEGRATION: 3. interneurons ( or relay neurons): MOTOR OUTPUT: 4. motor neurons: 5. Effector:

B2. The Reflex Arc reflex: rapid, unconscious response stimulus : a change in the environment that is detected by a receptor and elicits a response response: a reaction to a stimulus

A Pain Withdrawal Reflex Arc

Key Concept B: The Nervous System Links Stimulus to Response text p. 368-370

Vocabulary

1. _________

2. _________

3. _________

4. _________

5. _________

13

The CNS consists of two structures: C1. The Spinal Cord Functions of the spinal cord:

I. integrating center for spinal reflexes II. conducts sensory nerve impulses to the brain for

interpretation and motor nerve impulses from the brain to the effectors.

Structure of the spinal cord:

text p. 388 - 389: Read and edit the information

blood-brain barrier: cerebrospinal fluid: Explain how the blood-brain barrier and the cerebrospinal fluid protect the brain and spinal cord:

Key Concept C: The CNS integrates information text p. 385-395

Vocabulary

Vocabulary

14

C2. The Brain Functions of the brain: (text p. 391) cerebellum: medulla oblongata: pons: hypothalamus pituitary: cerebrum: ( text p. 387)

Structures of the brain:

Vocabulary

15

The Structure and Function of the Cerebrum Structure of the Cerebrum: The cerebrum is divided into two. Each half of the cerebrum consists of : (text p. 389)

• The cerebral cortex is highly folded. Grooves between folds are called fissures.

• The cerebrum is divided into two halves called cerebral

hemispheres. o the left hemisphere controls movement of the

right side of the body

o the right hemisphere controls movement on the left side of the body.

o It appears that In most people, the left

hemisphere is more important for language, numerical and scientific skills, and reasoning.

o It appears that the right hemisphere is more

important for musical and artistic awareness, spatial and pattern perception, recognition of faces, emotional content of language and creative thoughts and imagination.

• The two cerebral hemispheres are connected by the a

corpus callosum ,

o Function of the corpus callosum: text p. 391

Anterior Cross Section of the Brain

16

The cerebral cortex consists of four pairs of functional lobes. text p. 390 - 392 Major functions of the lobes: ( text p. 391) Frontal Lobe: Parietal Lobe: Temporal Lobe: Occipital Lobe:

Vocabulary

17

Key Concept D

: The Autonom

ic Nervous System

text p. 385-395

• Under involuntary control

• hypothalam

us and medulla

oblongata control the autonomic

system

• two divisions: sym

pathetic and parasym

pathetic •

Antagonistic: they have opposing functions

Sympathetic System

Parasympathetic System

- em

ergency situations - returns body to norm

al - “fight or flight”

- “rest and digest” - neurotransm

itter is - neurotransm

itter is norepinephrine

acetylcholine

18

Explain the differences between: text p. 406-408 sensory reception: sensation: perception: sensory adaptation:

E1. Types of Sensory Receptors text p. 408-409 Category and Type of Receptor

Examples of receptor

Stimulus

Photoreceptors vision

Chemoreceptors taste

smell

Mechanoreceptors touch/pressure/pain

hearing

balance

body position

Thermoreceptors temperature

Key Concept E: Sensory Receptors and Sensation

Vocabulary

19

F1. Photoreception: Sense of Sight

Diagram of the Eye

Structure and Function of the Eye - page 411

Structure Function sides/back of sclera

cornea

sides/back of choroid

iris

pupil

ciliary muscles

rods

cones

fovea

lens

humours

optic nerve

Key Concept F: Sense organs link the environment to the nervous system

Vocabulary

20

Focusing text p. 412 • Image formation on the retina involves refraction of light

rays by the cornea and lens, which focus an inverted image on the central fovea of the retina.

How the lens changes shape in order to focus:

• For viewing near objects, the lens becomes rounder (increases its curvature) : ciliary muscles contract and suspensory ligaments relax

• For viewing far objects, the lens becomes flatter

(decreases its curvature) : ciiary muscles relax and the suspensory ligaments become taut

accommodation: Blind Spot: Sensory Adaptation:

Human Retina

Vocabulary

21

Differences between

rods and cones in l ight and dark adaptation

text p. 414-415 RODS CONES

Conditions Affecting the Cornea and Lens text p. 412-413 Astigmatism: Myopia:

Hyperopia: Cataracts: Technology Used to Correct Eye Defects Technology Name Technology

Description Use of Technology

Cataract Surgery -removal of the cataract -repaired with artificial lens

-used to treat a cataract which makes the lens cloudy

Corrective Lenses -glasses or contact lenses focus light at the correct location on the retina

-used as a treatment for poor visual acuity

Laser Surgery -cells of the cornea are shaved by a laser beam -adjustment is permanent and not reversible

-corrects myopia or hyperopia

Vocabulary

22

Dissection of an Eye text reference p.417 The human eye and pig eye are very similar in structure and function. In this investigation, you will dissect a real pig eye to gain a better understanding of how the structures of the eye relate to their functions. Question How do the structures of a pig eye relate to their functions? Materials pig eye scissors paper towel dissecting tray scalpel disinfecting powder pointer Procedure 1. Put on apron. Place pig eye on the dissecting tray. 2. Examine and locate the sclera, cornea, and optic nerve on the back

of the eye. 3. Trim away the excess tissue surrounding the eyeball on the sclera. 4. Hold the eyeball gently with your thumb and forefinger at the

cornea and near the optic nerve. Set the eyeball down on the paper towel and cut a cross section of the eye by making an incision slightly behind the middle of the eyeball through the sclera. Apply light slicing cuts as you begin to penetrate the eye.

5. Some of the vitreous humor, fluid from the interior of the eye, may begin to ooze out of the eyeball as you cut through the sclera. If it does, this is normal and not a problem.

6. Once you have made a cross-sectional cut around the eyeball, separate it

into halves. Let the vitreous humor, and any associated structures, slowly slide out of the eye. The lens may slide out along with the vitreous humor. Identify and examine the lens. Notice when you hold the lens in your hand and look through the lens at your lab partner, the image of your partner is upside down!

7. Identify the white sclera (external layer), the black choroids layer (intermediate layer), and thin retina (internal layer). Follow the retina layer to its convergence at the back of the eye to form the optic nerve. This is called the blind spot.

8. Examine the anterior (front) chamber of the eye. Identify the large, central lens ( if it did not slide out already), as well as the circular ciliary muscle and suspensory ligament attached to it. The aqueous humor is the fluid in the anterior chamber. Identify the iris and the pupil. Identify the cornea.

SKETCHES & QUESTIONS – on a separate page A. Coronal Cross Section: Anterior View Sketch the anterior view of your pig eye. Examine the diagram on page 417 to understand an anterior perspective. Label the choroid layer, ciliary muscle and pupil. Do not use the diagram we labeled in class as that diagram is a sagittal section and you dissected a coronal cross section. B. Coronal Cross Section: Posterior View Sketch the posterior view. Examine the diagram on page 417 to understand a posterior perspective. Label the optic nerve and retina. Indicate where the 'blind spot' would be found. C. Which of your labeled structures contains the rod and cone cells? D. List the functions of the rods. E. List the functions of the cones. 9. Dispose of the pig eye and clean your dissecting tray and work area.

WASH your hands with soap and water!

Safety Precautions • Handle scalpels & scissors with care. • Wash you hands well when you are

finished. • Clean the dissection equipment when you

are finished – do not use hot water to clean the trays

23

F2. Mechanoreception: Sense of Sound and Balance

Structure and Function of the Ear text p. 420

Structure Function pinna

auditory canal

tympanum

ossicles

oval window

cochlea

organ of Corti

auditory nerve

semicircular canals

Eustachian tube

Diagram of the Ear

24

Describe how the structures of the human ear support the function of hearing: text p. 419-424 • Sound waves enter the auditory canal, strike the eardrum,

pass through the ossicles, strike the oval window, set up waves in the fluid of the inner ear and stimulate hair bundles (great picture on p.421!) in the organ of Corti

• Hair cells convert mechanical vibrations into nerve impulses • Nerve impulses travel through the auditory nerve to the

cerebrum (temporal lobe) for interpretation

Organ of Corti

Describe how the structures of the human ear support the function of balance: text p. 424

1. Head position relative to gravity: standing upright without losing our balance (This type of balance is maintained by the utricle and saccule)

2. Body movement: moving without losing our balance in

response to rotation, acceleration, deceleration. This type of balance is maintained by the semicircular canals

Various neuron pathways between the cerebellum and cerebrum (motor area of the frontal lobe) play a key role in maintaining balance. The cerebellum monitors the information and makes corrective adjustments in the motor activities that originate in the cerebrum. Utricle & Saccule Semicircular Canals

Technology Used to Correct Ear Defects Technology Name Technology

Description Use of Technology

Hearing Aids -amplifies sound waves

-used to increase sensory neural stimulation

Cochlear Implants -translates sounds into electronic signals than can be interpreted by the brain

-useful for people with deafness caused by a disorder or an injury that destroyed hair cells in the cochlea

25

Mechanoreception: Sense of body position

text p.424-425 Mechanoreception: Proprioceptors: F3. Thermoreception: Sense of heat and cold text p.427 Perception of heat/cold/pain/touch/pressure:

• sensory receptors in the skin respond to some type of stimuli and generate an action potential

F4. Chemoreception Sense of taste text p.425-426

• The tongue contains chemoreceptors for the sense of taste. • Before a substance can be tasted, it must be dissolved in saliva. • Sensory adaptation occurs in both taste and smell • Taste buds respond to chemical stimulation of various tastes

(eg.: salty, sweet, bitter, sour) by generating an action potential, thus initiating the taste response

Sense of smell text p.426

• The nose contains chemoreceptors for the sense of smell (olfaction)

• Olfactory chemoreceptors respond to chemical stimulation of an odor molecule by generating an action potential, thus initiating the olfactory response.

Vocabulary

26

Nervous System Notes / Questions