1. Nervous System

2. The Nervous System Parts:
Brain, spinal cord, nerves, sensory receptors
Subdivisions:
Central Nervous System (CNS)
Peripheral Nervous System (PNS)
Autonomic – involuntary
Sympathetic – “fight or flight” responses
Parasympathetic – “rest & relax” responses
Enteric- “brain in the gut”
Somatic - voluntary
Functions…
Sensory perceptions, mental activities, stimulating muscle movements, regulates secretions of glands

3. Central Nervous System
Consists of brain and spinal cord
The structural & functional center of the entire nervous system which integrates incoming pieces of information & initiates an outgoing response

4. Peripheral Nervous System
All bodily nerves
Afferent (sensory)
Efferent (motor)
All pathways going toward and away from the CNS

5. Nervous System Organization

6. Cells of Nervous System
Neurons or nerve cells
Receive stimuli and transmit action potentials (electrical current)
Organization
Cell body or soma
Dendrites: input
Axons: output
Myelin or No myelin
Glia cells ( 5 types)
Support, clean, provide nutrition and protect neurons
Did you know? There are 100 billion neurons in the brain, but there are about 10 to 50 times that many glial cells in the brain

7. Types of Neurons Functional Classification Structural Classification
Sensory or afferent: action potentials toward CNS (receives stimuli; could be a special sense organ)
Motor or efferent: action potentials away from CNS (attached to a muscle or gland)
Interneurons or association neurons: within CNS from one neuron to another
Structural Classification
Bipolar: a single axon and dendrite arise at opposite poles of the cell body. Found only in sensory neurons, such as in the Retina, Olfactory and auditory systems
Unipolar: a single process or fibre which divides close to the cell body into two main branches (axon and dendrite). These are also sensory neurons
Multipolar: has numerous cell processes (an axon and many dendrites). These are Motor neurons

8. More about the neuron… 1 substance effects the Speed of the Impulse!
Myelinated axons
Myelin protects and insulates axons from one another
Not continuous
Nodes of Ranvier
Impulse “jumps” from node to node
Fast impulse
Unmyelinated axons
Slower impulse
“Saltatory Conduction”

9. How Neurons Send An Impulse
Cells produce electrical signals called action potentials
Transfer of information from one part of body to another
Electrical properties result from ionic concentration differences across plasma membrane and permeability

10. Nerve Impulses – Making the Electricity
Resting Vs. Action Potential
Resting Potential
Concentration of K+ higher inside than outside cell
Na+ higher outside than inside

11. Nerve Impulses: Flow of the Electrical Current
Propagation of Action Potential
Ions (charged particle)
Na+ (moves inside only)
K+ (moves outside only)
A wave of electrical fluctuation that travels along the plasma membrane; due to changes in chemical concentrations by ions

12. Action Potentials
Series of permeability changes when a local potential causes depolarization of membrane
Phases
Depolarization
More positive
Repolarization
More negative
All-or-none principle
Neuron will fire or it won’t

13. The Synapse Junction between two cells
Electrical message transferred across the synapse by chemicals called neurotransmitters

14. How is an electrical impulse ignited? One Word:Stimulus
Any change in your environment.
Temp, sound, smell
You may or may not respond to a specific stimulus

15. What receives the Stimulus? Sensory Receptors
In order for a stimulus to be detected, it must be strong enough to elicit an impulse
It must be at the threshold level- the minimum stimulus to start an impulse
The all-or-none response means that either a neuron will fire or it won’t, there is no partial impulse
Sensation- the brain’s interpretation of what the stimulus is

16. Classification of Receptors
Mechanoreceptors- activated by mechanical stimuli or deformation of the receptor
Chemoreceptor- changing of the chemical concentrations around the body
Thermoreceptors- detect hot and cold
Nociceptors- any stimuli that can cause tissue damage; sensation of pain
Photoreceptors- respond to light

17. Receptors, Stimulus, & Body Actions
A Stimulus ignites a Receptor
The Receptor receives the message that the Stimulus is sending
The message is sent and a Body Action occurs
There are three kinds of actions that our body carries out, namely voluntary actions, involuntary actions or reflex actions and conditioned reflex actions. All three actions involve stimuli, an impulse, neurons and effectors. However they do have their differences.
A reflex is a direct connection between stimulus and response, which does not require conscious thought.
Voluntary Reflex is one of your own free will or design; done by choice; not forced or compelled.

18. Body Actions
Voluntary Actions: A voluntary action is basically an action in which you initiate by your own conscious.
For example, when you see a friend over at the other side of the room, you wish to attract the attention of that friend of yours, hence you may want to wave your hand and call out his name. This is done by your brain by sending impulses from it to the effectors or in this case, your biceps and triceps muscles and also your larynx, via relaying neurons, the spinal cord, synapes and motor neurons. The impulses upon reaching their respective effector muscles cause the waving of your hand and you to shout out your friend's name. This action is under the control of the will thus is known as a voluntary action.
Involuntary Actions (Reflex Actions): A voluntary action is under the control of one’s will, involuntary actions as their name suggest, are total opposites of voluntary actions.
In this case, your spinal cord or your brain takes total control, without your own conscious, depending on where the stimuli originate. Reflex actions controlled by the spinal cord, example scratching, are called spinal reflexes while those by the brain, example blinking, are called cranial reflexes. Blushing, sneezing and salivation are also reflex actions however, salivation is also known an conditioned reflex action.

19. Reflexes
A reflex is a response to a perturbing stimulus that acts to return the body to homeostasis. This may be subconscious as in the regulation of blood sugar by the pancreatic hormones, may be somewhat noticeable as in shivering in response to a drop in body temperature; or may be quite obvious as in stepping on a nail and immediately withdrawing your foot.
Reflexes require a minimum of two neurons, an sensory neuron (input) and a motor neuron (output).
The sensory neuron (such as a pain receptor in the skin) detects the stimuli and sends a signal towards the CNS. This sensory neuron synapses with a motor neuron which innervates the effector tissue (such as skeletal muscle to pull away from the painful stimuli). This type of reflex is the "withdrawal" reflex and is monosynaptic, meaning only one synapse has to be crossed between the sensory neuron and the motor neuron. It is the simplest reflex arc and the integration center is the synapse itself. Example: Tendon Jerk

20. Reflexes
Polysynaptic reflexes are more complex and more common. They involve interneurons which are found in the CNS. More complex reflexes may have their integration center in the spinal cord, in the brainstem, or in the cerebrum where conscious thoughts are initiated.
In humans: the polysynaptic reflex is the sudden movement to protect life and limb. An example usually given is walking in a shallow pond and stepping on a sharp object. The foot immediately raises before you are voluntarily aware of pending danger. It is more complex than the monosynaptic reflex because prolonged output from the spinal cord is needed to process “Am I in danger? or Am I hurt?” The monosynaptic reflex doesn’t need the process time to initiate a “stretch or jerk”.

21. Reflex Arc
A predictable response to a stimulus which may or may not be conscious
A reflex consists of either muscle contraction or glandular secretion
Neurons involved in reflex
Afferent neuron- sensory
Interneuron
Efferent neuron- motor
Process:
1) Detection of signals from outside environment or detection of deviation change) from homeostasis from internal environment.
2) Integration of multiple signals from outside and inside to produce appropriate response.
3) Response to counteract stimulus being detected

22. Reflexes Vs. Reactions
Many people consider only the simplest types of responses as "reflexes", those that are always identical and do not allow conscious actions.
We must not confuse these with "reactions", which are different from reflexes in that they are voluntary responses to a stimulus from the environment.
For example, while the body has various subconscious physiological responses to mitigate cold, as humans we can simply choose to put on more clothes. This is a conscious order made by the cerebrum, not an involuntary response to a stimulus. This is a very complex response involving millions of neurons and some time to process the voluntary response.
In contrast, spinal reflexes occur much faster, not only because they involve fewer neurons, but also because the electrical signal does not have to travel to the brain and back. Spinal reflexes only travel to the spinal cord and back which is a much shorter distance. Because of this and the complexity of conscious reactions, they take more time to complete than a reflex. On average, humans have a reaction time of 0.25 seconds to a visual stimulus, 0.17 for an audio stimulus, and 0.15 seconds for a touch stimulus. Did your reaction time fall within the average during the Reaction Time Lab?
Reaction times vary from individual to individual. Because of the higher degree of neural processing, reaction times can be influenced by a variety of factors. Reaction times can decrease with practice, as often times athletes have faster reaction times than non-athletes. Sleepiness, emotional distress, or consumption of alcohol can also impact reaction time.

23. Organization of the Brain
What about the processing/integration center OR better known as the BRAIN!
Organization of the Brain
Hindbrain
Adjacent to top part of spinal cord
Midbrain
Rises above hindbrain
Forebrain
Uppermost region of brain

24. Hindbrain
Medulla
Controls vital functions, such as breathing and heart rate
Regulates reflexes
Cerebellum
Plays important role in motor coordination
Pons
Involved in sleep and arousal

25. Midbrain
Brain stem
Includes much of hindbrain (but not cerebellum) and midbrain
Determines alertness
Regulates basic survival functions
Reticular Formation
Involved in stereotyped patterns of behavior, such as walking and sleeping

26. Forebrain: Limbic System, Thalamus, & Basal Ganglia
Important in both memory and emotion
Two principal structures
Amygdala
Involved in discrimination of objects necessary for survival
Hippocampus
Has special role in storage of memories
Thalamus
Serves as relay station for information
Basal Ganglia
Works with cerebellum and cerebral cortex to control and coordinate voluntary movements

27. Forebrain: Hypothalamus
Monitors . . .
eating, drinking, sex
emotion, stress, reward
Helps direct endocrine system
Regulator of body’s internal state
Involved in pleasurable feelings

28. Forebrain: Cerebral Cortex
Somatosensory Cortex
Located at front of parietal lobes
Processes information about body sensations
Motor Cortex
Located just behind frontal lobes
Processes information about voluntary movement
Association Cortex
Makes up 75% of cerebral cortex
Integrates information
Occipital lobes
Responding to visual stimuli
Temporal lobes
Hearing, language processing, memory
Frontal lobes
Personality, intelligence, control of voluntary muscles
Parietal lobes
Registering spatial location, attention, motor control

29. Last but NOT Least…. Spinal Cord
PORTAL for the nerve pathways that carry information from the arms, legs, and rest of the body, and carries signals from the brain to the body.