THE BRAIN AND THE SENSESSECTIONS 35-2 and 35-3

What were the divisions of the nervous system?• Central Nervous System

a. Brain and Spinal Cord

b. Interprets all information from sensory nerves and sends responses to the motor nerves.

• Peripheral Nervous System

a. Sensory nerves – 5 senses, picks up stimuli and sends to CNS.

b. Motor nerves – voluntary or involuntary, carries out response sent by CNS.

Neuron types: Sensory, Interneurons, Motor

The Brain• Consists of mainly interneurons• Five main structures:

1. Cerebrum – largest section, intelligence, learning and judgment. All voluntary activities.

2. Cerebellum – coordination of voluntary movements.

3. Brain Stem – controls vital functions for life

4. Thalamus – Relay station for incoming sensory info.

5. Hypothalamus – Controls hunger, thirst, fatigue, body temperature.

Comparing Human, Dog and Rat Brains

Cerebrum• Two hemispheres

connected by the corpus callosum

• Four Lobes:• Frontal – movement,

problem solving, rational, personality

• Parietal – sensations and perceptions

• Occipital – vision• Temporal – hearing,

language, memory

Functions of the Cerebrum

Brain StemThree sections:1. Midbrain 2. Pons 3. Medulla

Oblongata –regulates heart rate, blood pressure, respiration, coughing, sneezing, vomiting, swallowing

Spinal Cord• Thick rope of interneurons • Main communication line to brain• 31 pairs of spinal nerves• Herniated disc – swelling of

intervertebral discs, pinches spinal nerves

Paralysis is when movement in lost. Depends on where the cord/nerve is injured.

Rapid, automatic responses to specific stimuli.

Their purpose is to preserve homeostasis.

Only a few neurons are needed.

Why do doctor’s test reflexes?

What is the advantage of having reflexes?

Reflexes

THE SENSESSection 35-4

The Senses• Part of the PNS – sensory division• Five types of sensory receptors:

1. Pain receptor

2. Thermoreceptor

3. Mechanoreceptor

4. Chemoreceptor

5. Photoreceptor• 5 organs for sensory perceptions

Where in the body are these receptors located and what type of stimulus do they respond to?

The SkinThe Skin1. Touch and

Pressure (mechanoreceptors)

- Light and strong receptors

2. Temperature (thermoreceptors) - Warm and cold free nerve endings

3. Pain Receptors

(nociceptors) - Respond to all types of stimuli

The Eye• Rods and cones are the

photoreceptor cells• Located in the retina • Rods – peripheral and low

light vision• Cones – color vision and

greatest acuity• Optic nerve sends signals

to brain; no photoreceptors

Where are all the parts of the eye? Their functions?

The Ear• Mechanoreceptors are ciliated

cells• Function: hearing and balance• Hearing comes from cochlea

- vibrations in air are conducted to the: tympanum to ossicles to

cochlea to auditory nerve to brain

• Balance come from semi-circular canals

- bending or rotating of head moves fluid in canals

Eustachian tube – equalizes pressure, connects with throat

SmellingSmelling• Chemoreceptors – stimulated by chemicals• Olfactory cells – sensory cells for smell• Low threshold (only a few molecules needed to detect)• Watery mucus lines cells to act as solvent.• Olfactory bulb sends impulses to olfactory cortex region of brain.

• Anosmia – loss of sense of smell• Helps with taste perception.

Taste• Chemoreceptors – picks up chemical

stimuli• Molecules must be dissolved in a solvent

to activate receptors.• Saliva is the solvent! • Taste receptors are called “gustatory

cells”• Gustatory cells found in taste buds all

over tongue/mouth• So, a single taste bud has many gustatory cells.

• 5 main tastes: salty, sweet, sour, bitter, umami