Nervous System and The Brain

The Nervous System Subdivided into two categories: Central Nervous System Contains brain and spinal cord Peripheral Nervous System Nerves and ganglia outside of CNS Reflexes A hot stove

The Nervous System The nervous system has a coordinating role where it receives, processes, stores, and transmits information that comes from the body and the outside world The neuron is the basic unit (cell) of the nervous system Impulses (signals) are carried throught the body by nerves

Neurons Dendrite receives impulses Axon propagates the impulses Longest neuron in the body? Sciatic nerve which connects toes to spinal cord

Neurons The neurons are the only cells that react to a stimulus A stimulus is a change in the environment that results in nerve excitation Ex. sun shining in your eyes or hearing a sound Nerves are structures that help transmit information between the central nervous system and the various regions of the body https://www.youtube.com/watch?v=Ibzfwtdtong

Transmitting Signals Neurons must pick up stimuli, transform them into nerve impulses and then transmit these impulses on to the next neuron A nerve impulse is therefore any electric signal transmitted by a neuron As signals move from one neuron to another, they must cross the synapse. This is the transition zone between two neurons (a very small gap)

Basic Tasks of the Nervous System Sensory Input: Monitor both external and internal environments. Integration: Process the information and often integrate it with stored information. Motor output: If necessary, signal effector organs to make an appropriate response.

Nervous System Composed of CNS and PNS The central nervous system is made of the brain and the spinal cord

The Brain Some brain myths… http://www.popsci.com/10-brain-myths-busted?image=0 https://www.exploratorium.edu/hockey/saves2.html

The Brain The brain controls everything in the body The brain contains more than 100 billion neurons (nerve cells) and is the biggest part of the central nervous system

Size isn’t everything… Neanderthal brains had more capacity devoted to vision and body control, with less left over for social interactions and complex cognition Morton – racist brain size study http://www.smithsonianmag.com/science- nature/science-shows-why-youre-smarter-than-a- neanderthal-1885827/

Parts of the Brain The Brain has three main parts… Cerebrum Cerebellum Medulla oblongata (brain stem)

Concussions https://www.youtube.com/watch?v=tgChTeALF7g Fencing response

The Cerebrum The largest part of the brain It controls your: Thinking Memory Speaking Movement Identifies info gathered by your sensory organs

Lobes of the Brain The cerebrum is divided into several lobes, each of which is responsible for different tasks The frontal lobes are responsible for problem solving and judgment and motor function.

Lobes of the Brain The parietal lobes manage sensation, handwriting, and body position. The temporal lobes are involved with memory and hearing (short + long term) The occipital lobes contain the brain's visual processing system. (eyes + nostril ex)

The Cerebellum Below and to the back of the cerebrum. Controls your balance and posture (along with inner ear)

Medulla Oblongata (Brain Stem) Connects the brain to the spinal cord Controls heartbeat, breathing and blood pressure Responsible for certain reflexes: coughing, swallowing, hiccups, vomiting, and sneezing

Grey vs White Matter The brain can be divided into two types of tissue

Grey Matter The part of the brain controlled by nerve cell bodies and dendrites. It is grey in appearance and is where the true processing occurs Makes up 40% of the human brain and requires 94% of available oxygen

White Matter Composed of axons Found in the center of the brain and between the brain stem and cerebellum Facilitates communication between the grey matter of the brain and between the brain and the rest of the body Makes up 60% of the human brain

Spinal Cord Connects the brain to the rest of the nervous system. Sends messages to and from the brain. The spinal cord is protected by small bones called vertebrae

Vertebrae

Peripheral Nervous System (PNS) Consists of all the nerves that leave the spinal cord or brain reaching all parts of the body. It has 2 types of nerves Sensory nerves – sending info to CNS Motor nerves – sending info to muscles

Types of Action PNS has 3 types of actions: Voluntary acts Involuntary acts Reflexes

Voluntary Acts This system contains the skeletal muscles Responsible for the conscious control of our movement Signals from the brain effectuate contractions of the muscles

Involuntary Acts An action that occurs without conscious thought or choice Breathing, hiccups, digestion, coughing, sneezing

Reflex https://www.youtube.com/watch?v=qpw31bvoLpg Is an involuntary automatic reaction that happens without thinking about it, due to an external stimulus A reflex happens quickly in less than a second. The difference between a reflex and an involuntary action is that a reflex requires a stimulus (external factor)

Reflex Arc

The brain is not involved in a reflex. Sensory Receptor (responds to a stimulus by producing a impulse) Sensory Neuron (axon conducts impulse) Integrating Center (Relay impulse from sensory to motor neurons) Motor Neuron (axon conducts impulse to effector) Effector (muscle that responds to A motor nerve impulse)