Animal structure and function

The nervous system

Parts of the nervous system

43C, 44B, 45D

Brain structure and function

Retina

Eyes

Neurons:

How neurons communicate:

Resting potential: The resting membrane potential of a neuron is about -70 mV (mV=millivolt) - this means that the inside of the neuron is 70 mV less than the outside. At rest, there are relatively more sodium ions outside the neuron and more potassium ions inside that neuron. The resting potential arises from two activities.

• The Na-K ATPase pump

• Leaky K+ channels

• Leaky Na+ channels

K+

NaNa

NaNa+

K+K+

K+K+

K+

The potentials

• The resting potential

• The threshold potential

• The action potential

• The refractory (Undershoot)

The resting potential is the resting membrane potential of a neuron is about -70 mV, the imbalance of electrical

charge that exists between the interior of electrically excitable nerve cells and their surroundings.

The threshold potential is the critical level to which a

membrane potential must be depolarized to initiate an action

potential. Threshold potentials are necessary to regulate and

propagate signaling in both the central nervous system and

the peripheral nervous system.

Action potential

• Depolarization: Na channels open

• Repolarization: Na channels close and K channels open

The refractory (Undershoot): A refractoryperiod occurs during the undershoot phase; during this period, the neuron is insensitive to depolarizing stimuli.

The potentials

• The resting potential

• The threshold potential (yellow)• The action potential (green) (light blue)• The refractory (Undershoot) (light blue)

• The Na-K ATPase

pump

• Leaky K+ channels

• Leaky Na+

channels

The membrane

potentials (mV)

The resting

potential

Na+ in =K+ out -70

The threshold

potential (yellow)

Na+ in > K+ out -55

The action

potential (green)

(light blue)

1. Depolarization: Na+ in >>> K+ out2. Repolarization: Na+ in

C

The potentials

• The resting potential -D

• The threshold potential

• The action potential-A (1)

• The refractory (Undershoot)-C

Schwann cells show remarkable versatility in undertaking a broad repertoire of functions. Ensheathment and

myelination are specifically regulated by contact with axons, and the Schwann cell is centrally involved in

extracellular matrix production in the peripheral nerve system (PNS) trunk. Additional Schwann cell functions

include the promotion of both peripheral and central nervous system regeneration, provision of a versatile source

of trophic factors, the capacity to remyelinate central nervous system axons, and the restoration of

electrophysiological conduction. Since it is now possible to isolate Schwann cells both from neonatal and adult

human peripheral nerve, their ability to promote regenerative efforts by many central neurons suggests a role for

Schwann cell autografts in influencing central nervous system repair.

Myelinating Schwann cells wrap around axons of motor and sensory neurons.

USABO2011,24C

Neurotransmitter: When an impulse reach the end of axon releases a chemical called a Neurotransmitter into the space between the two neurons/between a

neuron to a muscle . This space is called a synapse.

Neurotransmitter: Acetylcholine

Acetylcholine is the neurotransmitter produced by neurons referred to as cholinergic neurons. In the peripheral nervous system acetylcholine plays a role in skeletal muscle movement, as well as in the regulation of smooth muscle and cardiac muscle. In the central nervous system acetylcholine is believed to be involved in learning, memory, and mood.

Acetylcholine is synthesized from choline and acetyl coenzyme A through the action of the enzyme choline acetyltransferase and becomes packaged into membrane-bound vesicles . After the arrival of a nerve signal at the termination of an axon, the vesicles fuse with the cell membrane, causing the release of acetylcholine into the synaptic cleft . For the nerve signal to continue, acetylcholine must diffuse to another nearby neuron or muscle cell, where it will bind and activate a receptor protein.

Acetylcholine is synthesized from choline and acetyl coenzyme A through the action of the enzyme choline acetyltransferase

Low synaptic concentrations of acetylcholine can be maintained via a hydrolysis reaction catalyzed by the enzyme acetylcholinesterase. This enzyme hydrolyzes acetylcholine into acetic acid and choline.

If acetylcholinesterase activity is inhibited, the synaptic concentration of acetylcholine will remain higher than normal. If this inhibition is irreversible, as in the case of exposure to many nerve gases and some pesticides, sweating, bronchial constriction, convulsions, paralysis, and possibly death can occur.

1

1

2

2

Norepinephrine

GABA: the major inhibitory neurotransmitter in the central nervous system

D

A

The circulatory system can either be open or closed, depending on whether the blood flows freely in a cavity or is contained in vessels.

A closed circulatory system,

found in all vertebrates and

some invertebrates,

circulates blood

unidirectionally from the

heart, around the body, and

back to the heart.

An open circulatory system, found in arthropods, pumps blood into a cavity called a hemocoel where it surrounds the organs and then returns to the heart(s) through ostia (openings).

The circulatory system can either be open or closed, depending on whether the blood flows freely in a cavity or is contained in vessels.

USABO2012, 50C

Human circulatory system

Components of Blood

Component Scientific name Property

Plasma Liquid port of bloodContains clotting factors, hormones, antibodies, Dissolved gases, nutrients, and wastesMaintains proper osmotic potential of blood, 300mosm/L

Red blood cells(RBCs)

Erythrocytes Carry hemoglobin and oxygenDo not have a nucleus and live only about 120 dayFormed in bone marrow and recycled in liver

White blood cells (WBCs)

Leukocyte Flight infection and formed in bone marrow

Platelets Thrombocytes Component of blood whose function is to stop bleeding by clotting blood

The Human Red Blood Cell SmearUSABO2012, 26E

USABO2012, 26E

Components of Blood

Component Scientific name Property

Plasma Liquid port of bloodContains clotting factors, hormones, antibodies, Dissolved gases, nutrients, and wastesMaintains proper osmotic potential of blood, 300mosm/L

Red blood cells(RBCs)

Erythrocytes Carry hemoglobin and oxygenDo not have a nucleus and live only about 120 dayFormed in bone marrow and recycled in liver

White blood cells (WBCs)

Leukocyte Flight infection and formed in bone marrow

Platelets Thrombocytes Component of blood whose function is to stop bleeding by clotting blood

USABO2013, 36C

F. O-

Human heart

Pathway of blood

Blood enters the heart through

1. Vena cava (1). From there it continues to the:

2. Right atrium ( then pass right AV valve-tricuspid valve)

3. Right ventricle (then pass pulmonary valve)

4. Pulmonary artery

5. Lung

6. Left pulmonary veins

7. Left atrium (then pass left AV valve-bicuspid valve)

8. Left ventricle (then pass Aortic valve)

9. Aorta

10. body

Pathway of blood

Label the diagram using these labels

Aorta Pulmonary vein

Right atrium Left atrium

Right ventricle Pulmonary artery

Left ventricle Vena cava

Activities

1. Left side of the heart is red, because the blood contains more O2.

2. Right side of the heart is blue, because the blood contains more CO2.

Describe the route of the blood through the heart. This has been started for you below:Vena cava

Campbell biology

Figure 42.10

USABO2011, 27A

Lung and gas exchange in human

Lung and gas exchange in human

Lung and gas exchange in human

USABO2013, 24B

Circulatory and respiration system in human

USABO2011, 21B

USABO2012, 38C

Amniotic egg (reptile/bird vs mammal)

Notochord: A cartilaginous skeletal rod supporting the body in all embryonic and some adult chordate animals

15B,16A

17B,18E,20A,21B

B

22B,23E,24C