Chapter 38.1-38.3 The Nervous System

Nervous systems are the most intricately organized data-processing on Earth.

Has 3 interconnected functions:

1) Sensory Input

2) Integration

3) Motor Output

1. Sensory input – conduction of signals from sensory receptors to processing centers in brain & spinal cord

Sensory receptors include:

Pain receptors sense dangerous stimuli.

Thermoreceptors detect heat or cold.

Mechanoreceptors respond to mechanical energy (such as touch,

pressure and sound).

Chemoreceptors respond to chemicals.

Electromagnetic receptors respond to electricity, magnetism, and light

(sensed by photoreceptors).

1)Pain receptors 2)Thermoreceptors 3)Mechanoreceptors 4)Chemoreceptors 5)Electromagnetic receptors

2. Integration – the interpretation of sensory signals & the formulation of responses within processing centers

3. Motor output – conduction of signals from a processing center to effector cells that perform the body’s responses (muscle cells)

Sensory Input = lack of food in stomach

Integration = realization that you are hungry

Motor Output = eating nasty hot dogs

Divisions of the Nervous System

• Central Nervous System (CNS) consists of the brain & spinal cord

• Peripheral Nervous System (PNS) consists of communication lines called nerves that carry signals into & out of the CNS

Central

Nervous System

Peripheral

Nervous System

Vertebrate Central Nervous System

• Consists of the brain & spinal cord

- spinal cord receives sensory information from the skin & muscles and sends out motor commands for movement

- brain is the system’s master control center

•Fluid-filled spaces in the brain are called ventricles and are continuous w/the central canal in spinal cord

- ventricles & central canal contain cerebrospinal fluid: it cushions the CNS & supplies it w/nutrients, hormones, & removal of wastes

•CNS has 2 distinct regions

- white matter consists of axon & dendrites

- gray matter is mainly nerve cell bodies

Vertebrate Peripheral Nervous System

• Has sensory & motor functions

- cranial nerves-originate in the brain and terminate mostly in structures in the head or upper body

- spinal nerves-originate in spinal cord and extend to parts of the body below the head

•PNS consists of 2 separate groups of cells

1. Sensory Nervous System (afferent) has neurons which bring info to the CNS from sensory receptors

2 DIVISIONS

1senses external environment

2senses internal environment

2. Motor/Autonomic Nervous System (efferent) carries signals from the CNS to the effector organs

a.Motor nervous system carries signals to skeletal muscles; voluntary (under conscious control) and consists of a reflex type of reaction

b.Autonomic nervous system regulates internal environment by controlling smooth & cardiac muscle and organs of the gastrointestinal, cardiovascular, excretory, and endocrine systems

3 Divisions of Autonomic NS

• 1Sympathetic nervous division: prepares the organism for action; speeds up heart rate, increases metabolic rate, dilates bronchi

• 2Parasympathetic nervous division: enhances activities that gain or conserve energy; slows heart rate, stimulates digestion, constricts bronchi

Brain develops from the enlargement & subdivision of 3 anterior bulges of the spinal cord.

3 Regions of the Brain

1. Hindbrain

-medulla

oblongata

-pons

-cerebellum

HINDBRAIN (3 parts) A. Cerebellum—Coordinates body movement; plays role in learning, decision-making, and remembering motor responses Brainstem (3 parts) *Conducts data to and from other brain centers; helps maintain homeostasis; coordinates body movement.

Components of brainstem: B. Medulla Oblongata—Controls breathing circulation, swallowing, digestion C. Pons—controls breathing These two together house all sensory and motor neurons passing between the spinal cord and forebrain.

2. Midbrain—Receives and integrates auditory data; coordinates visual reflexes; sends sensory data to higher brain centers

Midbrain

A. Thalamus B. Hypothalamus C. Cerebrum

3. FOREBRAIN (3 parts)

--Most intricate neural processing occurs here

A. Thalamus contains most of the cell bodies of neurons that relay info to the cerebral cortex

--sorts data into categories

--suppresses some signals and

enhances others

B. Hypothalamus (important in

homeostasis) controls pituitary

gland, regulates body temp.,

sex drive, blood pressure, hunger,

thirst, fight or flight response

--It also helps us experience

emotions such as rage and

pleasure.

--it also functions as a timing mechanism (biological clock) which produces our circadian rhythm— patterns that are repeated daily (sleep/wake cycles)

C. Cerebrum-Performs sophisticated integration; plays major role in memory, learning, speech, emotions; formulates complex behavioral responses. (most extensive portion of the cerebrum is the cerebral cortex)

Cerebral Cortex • Consists of right and left cerebral

hemispheres. Each having four lobes.

-Thick band of fibers called the corpus callosum connects the hemispheres allowing them to process info together

-clusters of neuron cell bodies

-Under the corpus callosum is the basal ganglia. What does ganglia mean?

- basal ganglia are important in motor coordination

- degeneration of these nuclei occurs in Parkinson’s disease (causing the person to become passive & immobile)

•Circuitry of cortex produces our most distinctive traits.

- involved in reasoning, language, imagination, personality, etc.

- also assembles info received from ears, nose, eyes, taste buds, touch sensors

Right & left hemispheres specialize in different mental tasks—this is known as lateralization. - left is for language, logic, mathematical skills, as well as detailed skeletal motor control and processing fine visual and auditory details

- right is for imagination, spatial perceptions, artistic and musical abilities, emotions, pattern and face recognition

The Brain & Sleep

• Arousal - state of awareness of the outside world

• Sleep - state in which we receive external stimuli but we are not conscious of them

• Slow-wave (SW) sleep is characterized by delta waves (regular w/strong bursts of brain activity); when bedwetting & sleep walking occur

Sleep Waves

Rapid eye movement (REM) sleep

is when brain waves

are rapid and less

regular, more like

being awake; when

we dream

-REM sleep also appears to strengthen our ability to learn and remember repetitive skills -REM typically occurs about 6 times a night for 5-50 minutes at a time

Much of human emotion, learning, & memory depends on our limbic system. It is a functional unit of several integrating centers & interconnecting neuron tracts in our forebrain

Limbic System

Two key structures: 1) Amygdala-central in recognizing the emotional content of facial expressions and laying down emotional memories. 2) Hippocampus-involved in both the formation of memories and their recall

• Short-term memory usually lasts only a few minutes (look into a phone book for a # then dial it)

• Long-term memory is memorization & being able to apply it to current situations (commercials, faces)

Memory is the ability to store and retrieve information derived from experience. It occurs in 2 stages:

CHAPTER 39.1-39.2

Muscle Movement

Muscles

• found in antagonistic pairs

• connected to bones by tendons

• have a site of origin and insertion

ex: origin - biceps muscle attached to shoulder

insertion(place of work) - attached to forearm

Characteristics for Skeletal Muscles

Con. 39.1

• muscles can only contract, must be extended passively by antagonistic pair

• is a bundle of long fibers running the length of the muscle

•each fiber is a single cell w/many nuclei and mitochondria

Muscle Contraction (Sliding Filament Model)

• Parts of the muscle fiber:

- each fiber is a bundle of smaller myofibrils arranged lengthwise

- a myofibril consists of repeating units called sarcomeres

* produce the light & dark bands on muscle (this is what gives skeletal muscle its striated appearance)

p. 794

Sarcomere

• Z lines (made of thin microfilaments) are borders

• Light bands - made of thin filaments on edges of sarcomere

- thin filaments consist of a double strand of the protein actin & 1 strand of a regulatory protein

• Dark bands - made of thick filaments in the middle of sarcomere

- thick filaments consist of a number of parallel strands of the protein myosin

Sliding Filament Model

• proposed by A.F. Huxley

• sarcomere contracts (shortens) as thin filaments slide across thick filaments

• filaments don’t shorten

• a myosin head on thick filament binds to an actin monomer on the thin filament

• hydrolysis of an ATP molecule causes the myosin head to bend

•filaments will then slide past each other (similar to boat/oar)

•myosin head is released from the first actin monomer & attaches to a new one

* each head can move at about 5 movements per second

Characteristics for Cardiac Muscle

• found in heart

• striated

• generates its own action potentials w/out the help of the nervous system

Characteristics of Smooth Muscle

• found in the digestive tract

• lacks striations

• involuntary

• contractions are slow but can be sustained over long periods of time

Locomotion

• water: provides support against gravity but allows for a high frictional resistance

• air: provides little support for gravity but allows for low frictional resistance that requires us to have balance

- active travel from place to place

- requires us to overcome friction & gravity

Skeleton

Axial Skeleton: - skull (protects brain)

- backbone (protects spinal cord, supports appendages, gives body structure, s-shaped to help balance biped body)

- rib cage (protects lungs & heart)

Appendicular: - bones of the

appendages (arms, legs)

- bones that link appendages to axial skeleton (shoulder girdle, pelvic girdle)

- 3 functions: support, movement, protection

p. 801

Joints

• Ball-and-Socket - allows for rotation of arms and legs and moving in several planes

- ex: scapula-head of humerus (shoulder); pelvis-head of femur (hip)

p. 801

• Hinge - allows for movement in single plane

- ex: humerus-head of ulna (elbow)

• Pivot - allows for rotation

- ex: forearm at elbow, wrists

Bone Composition

• Outside Surface - covered w/fibrous connective tissue (when bones break or crack, this tissue is able to form new bone)

• Ends - cartilage replaces connective tissue to form cushions

• Bone Shaft - compact bone w/dense matrix surrounding a hollow cavity called yellow bone marrow (stored in fat)

- but at the end of the shaft is an inner layer of a spongy bone matrix called red bone marrow

- bone matrix: noncellular matrix of calcium salts (which resist compression) & protein fibers (which resist cracking) surround the cells secreting these materials

• bones begin to form about 1 month after conception and stop growing at about 18 yrs for women and 21 yrs for men

Skeletal Disorders

• Arthritis

- inflammation of joints

- affects 1 out of 7 in U.S.

- joints become stiff & sore, swell as cartilage between bones wear down or bones thicken at the joints (produces crunching noises when bones rub together & restrict movement)

- rheumatoid arthritis: joints become highly inflamed & the jointed tissues are destroyed by body’s immune system

* begins between 30-40 yrs old, usually more in women

* no cure, fitted w/artificial joints

• Osteoporosis

- bones become thinner, more porous, easily broken

- most common in women after menopause due to the decrease in estrogen (bone density starts decreasing between 30-35 yrs old)

- prevented by calcium intake and bone density exercises (running, walking)