C3.1: Integration of Body Systems

Brain Function (4)

Integrate information to regulate body functions

1. receives sensory info from sensory receptors (ex. sense organs like eyes or receptor cells in skin)

2. Processes Info, coordinates to make decisions

3. Stores info, utilizes memory

4. Sends instructions to respond, causes muscles to contract/glands to secrete

Spinal Cord

Part of CNS, located inside vertebral column (31 pairs of spinal nerves branch here)

Main Spinal Cord Tissues

white matter, myelinated axons

grey matter, cell bodies of motor and sensory neurons and interneurons, including synapses (typically cell body and dendrites, unmyelinated)

Spinal Cord Function

Processes info and handles unconscious processes like reflexes

Unconscious (5)

-awake or asleep

-performed involuntarily

-gland secretion and smooth muscle contraction

-coordinated by brain and spinal cord

-ex. food movement in esophagus

Conscious (5)

-only when awake

-performed voluntarily

-striated muscle contraction

-coordinated by cerebral cortex of brain (wrinkly part)

-ex. walking

Input into CNS

Happens via sensory receptors, convey messages from receptor cells to CNS. Receptors produce nerve inpulses (AP) that enter spinal cord via spinal nerves and brain via cranial nerves

Sensory Receptors

Located in sense organs and skin, some are specialized receptors like rods and cones (for eyes) and some are endings of neurons that act as receptors (touch)

Also located within body to maintain homeostasis, ex. stretch receptors in striated muscles to deduce posture and chemoreceptors in vessel walls to detect concentration of CO2 and O2.

Output from CNS

Occurs in motor neurons, primary motor cortex sends nerve impulses to control locomotion and maintain posture.

Cell bodies and dendrites located in grey matter of cerebral cortex, axon leads down to spinal cord (interneuron). This forms synapses with second motor neuron that leads to striated muscle, stimulating muscle contraction

Nerves

Bundle of nerve fibres (axons) in a protective sheath, vary in size and proportion of cells that are myelinated. Most contain both sensory and motor neurons.

Ex. sciatic nerve (down back of leg) and optic nerve

Reflex

Rapid, involuntary response to specific stimulus, simplest type of coordinated response, beneficial to survival by preventing injury.

Most reflexes only involve spinal cord (pain reflex), some involve brain (pupil reflex)

Pain Reflex Arc Process (5)

1. Receptor detects stimulus (pain), sensory nerve endings detect pain directly

2. Sensory neuron fires nerve impulse (AP), enters spinal cord via dorsal root and synapses with interneurons in grey matter

3. Interneuron, synapses with motor neurons and other interneuron that sends info to brain, combines impulses from multiple inputs and makes reflexes simple by often having only 1 interneuron between sensory/motor neurons

4. Synapses with Motor Neuron, AP leaves spinal cord via ventral root, impulses travel to same effector

5. Effector carries out response, muscles contract or glands secrete allowing movement from source of pain

General AP movement down neurons

Sensory neuron --> interneuron --> motor neuron

Cerebellum

"little brain" found in base of brain, underneath cerebral cortex. Controls skeletal muscle contraction, fine-tunes timing of contraction and maintains motor memory such as riding a bike