Biopsychology - the Nervous System

What is the Nervous System?

The functions of the Nervous system are: to [blank_start]co-ordinate[blank_end] the working of [blank_start]cells[blank_end] and [blank_start]organs[blank_end], to collect, process and [blank_start]respond[blank_end] to information in the [blank_start]environment[blank_end]. Consists of [blank_start]Central[blank_end] Nervous System and the [blank_start]Peripheral[blank_end] Nervous System

The Central Nervous System consists of the [blank_start]brain[blank_end] the [blank_start]spinal[blank_end] [blank_start]cord[blank_end]. The brain provides us with [blank_start]conscious awareness[blank_end]. It is divided into [blank_start]2[blank_end] hemispheres. It's [blank_start]outer[blank_end] layer is highly [blank_start]developed[blank_end]- called the [blank_start]cerebral cortex[blank_end]

The spinal cord is responsible for [blank_start]reflex[blank_end] [blank_start]actions[blank_end] (e.g. Pulling hand away from hot surface). Transfers messages to and from the [blank_start]brain[blank_end] and the [blank_start]rest of the body[blank_end].

The Peripheral Nervous System transmits messages to and from the [blank_start]Central[blank_end] Nervous System via [blank_start]neurons[blank_end]. Consists of 2 systems -[blank_start]somatic[blank_end] Nervous System and the [blank_start]autonomic[blank_end] Nervous System. The first of these controls muscle [blank_start]movement[blank_end] via [blank_start]motor[blank_end] [blank_start]pathways[blank_end] and sensory [blank_start]reactions[blank_end] via sensory [blank_start]receptors[blank_end].

The Autonomic Nervous System is involved in [blank_start]homeostasis[blank_end]. It is divided into 2 subsystems- the [blank_start]sympathetic[blank_end] NS and the [blank_start]para[blank_end]sympathetic NS. The fight or flight response happens when a [blank_start]stressor[blank_end] is detected, the [blank_start]hypothalamus[blank_end] triggers [blank_start]activity[blank_end] in the [blank_start]sympathetic[blank_end] branch of the ANS.

The Sympathetic Nervous System prepares the body to [blank_start]expend[blank_end] energy for fight or flight. By increasing [blank_start]heart[blank_end] [blank_start]rate[blank_end], slowing [blank_start]digestion[blank_end] and [blank_start]inhibiting[blank_end] [blank_start]saliva[blank_end] production. The Parasympathetic Nervous System is the [blank_start]resting[blank_end] state, it [blank_start]conserves[blank_end] energy. It has [blank_start]opposite[blank_end] actions to the Sympathetic NS as these systems are [blank_start]antagonistic[blank_end]. E.g. It reduces heart rate, increases digestion in the [blank_start]gut[blank_end], and [blank_start]stimulates[blank_end] saliva production in the [blank_start]salivary[blank_end] [blank_start]glands. [blank_end]

The Endocrine is made up of a [blank_start]network[blank_end] of [blank_start]glands[blank_end] that produce [blank_start]hormones[blank_end]. It's function is to [blank_start]secrete[blank_end] these hormones in order to [blank_start]regulate[blank_end] body functions - e.g. [blank_start]Metabolism[blank_end], [blank_start]promotes[blank_end] growth. Hormones are passed through the body through [blank_start]blood vessels[blank_end] that [blank_start]stimulate[blank_end] the [blank_start]corresponding[blank_end] receptor [blank_start]sites[blank_end]. The Endocrine system works alongside the [blank_start]Nervous[blank_end] System to control [blank_start]important[blank_end] body functions.

Label this diagram of the Endocrine system

The Pituitary gland is the '[blank_start]master gland[blank_end]' as it [blank_start]controls[blank_end] other glands, [blank_start]stimulating[blank_end] them to release [blank_start]hormones[blank_end]. For example, it produces a hormone called [blank_start]oxytocin[blank_end]- this induces [blank_start]contractions[blank_end] in [blank_start]labour[blank_end], so can be used to [blank_start]artificially[blank_end] [blank_start]induce[blank_end] labour. It is controlled by the [blank_start]hypothalamus. [blank_end]

The adrenal [blank_start]medulla[blank_end] within the adrenal [blank_start]gland[blank_end] releases [blank_start]adrenaline[blank_end] into the [blank_start]bloodstream[blank_end]. This causes the necessary [blank_start]physiological[blank_end] changes for the fight or flight response- the [blank_start]stress[blank_end] response. (Shows how [blank_start]Endocrine[blank_end] and ANS work together in stressful event).

Neurons are [blank_start]nerve[blank_end] [blank_start]cells[blank_end] that [blank_start]process[blank_end] and send messages [blank_start]electrically[blank_end] and [blank_start]chemically[blank_end]. Sensory neurons- called [blank_start]afferent[blank_end] nerves as they carry messages from [blank_start]sense[blank_end] receptors in the [blank_start]somatic[blank_end] NS in the [blank_start]Peripheral[blank_end] NS toward the [blank_start]brain[blank_end] and [blank_start]spinal[blank_end] [blank_start]cord[blank_end] in the [blank_start]Central[blank_end] NS. Found in sensory [blank_start]receptors[blank_end] in the body, such as [blank_start]eyes[blank_end], tongue.

Motor neurons are called [blank_start]efferent[blank_end] nerves as they carry messages [blank_start]away from[blank_end] the [blank_start]Central[blank_end] NS and to [blank_start]effectors[blank_end] such a muscles and [blank_start]glands[blank_end]. Relay neurons are found in the [blank_start]brain[blank_end] and [blank_start]spinal[blank_end] [blank_start]cord[blank_end]. [blank_start]Transfer[blank_end] messages from [blank_start]sensory[blank_end] neurons to [blank_start]motor[blank_end] neurons or other [blank_start]relay[blank_end] neurons.

Structure of a neuron: cell body/[blank_start]soma[blank_end]- includes a [blank_start]nucleus[blank_end] which contains the [blank_start]genetic[blank_end] [blank_start]material[blank_end] of the cell. Dendritea- [blank_start]branch[blank_end]-like structures that [blank_start]stick[blank_end] out from the cell [blank_start]body[blank_end] and carry messages from [blank_start]neighbouring[blank_end] neurons. Axon- [blank_start]tube[blank_end]-like 'arm' that electrical [blank_start]impulses[blank_end] travel down. Myelin sheath- [blank_start]fatty[blank_end] layer that [blank_start]surrounds[blank_end] and protects the [blank_start]axon[blank_end]. Also speeds up [blank_start]transmissions[blank_end] of impulses. Nodes of ranvier- gaps that [blank_start]segment[blank_end] the [blank_start]myelin[blank_end] [blank_start]sheath[blank_end] and speed up transmissions by forcing [blank_start]impulses[blank_end] to 'jump'. Terminal [blank_start]buttons[blank_end]- at the end of the [blank_start]axon[blank_end], they [blank_start]communicate[blank_end] with the next neuron.

Each neuron is separated by a gap called a [blank_start]synapse[blank_end], this includes the synaptic [blank_start]gap[blank_end]. Signals within neurons are transmitted [blank_start]electrically[blank_end]. Signals between neurons are transmitted [blank_start]chemically[blank_end] by [blank_start]synaptic[blank_end] [blank_start]transmission. [blank_end]

Impulse travels down axon until it reaches the pre synaptic terminal.

This triggers the release of neurotransmitter from the synaptic vesicles.

Neutrotransmitter is fired into the synaptic gap and bonds with receptor sites on dendrites of the post synaptic neuron

The impulse will continue to pass in this way via other neurons

Synaptic transmission... 1. Impulse travels down the [blank_start]axon[blank_end] until it reaches the [blank_start]pre[blank_end] [blank_start]synaptic[blank_end] [blank_start]terminal[blank_end] 2. This [blank_start]triggers[blank_end] the release of [blank_start]neurotransmitter[blank_end] from the [blank_start]synaptic[blank_end] [blank_start]vesicles[blank_end] 3. Neurotransmitter is fired into the [blank_start]synaptic[blank_end] [blank_start]gap[blank_end] and binds with [blank_start]receptor[blank_end] [blank_start]sites[blank_end] on [blank_start]dendrites[blank_end] of the [blank_start]post[blank_end] synaptic neuron. 4. The [blank_start]impulse[blank_end] will continue to [blank_start]pass[blank_end] in this way via other [blank_start]neurons.[blank_end]

Neurotransmitters can have either an excitatory or inhibitory effect on the next neuron. Excitatory neurotransmitter (e.g. [blank_start]Adrenaline[blank_end]) increase the [blank_start]positive[blank_end] charge of the next neuron, and [blank_start]increase[blank_end] the likelihood of it [blank_start]firing[blank_end]. Inhibitory neurotransmitter (e.g. [blank_start]Serotonin[blank_end]) increase the [blank_start]negative[blank_end] charge of the [blank_start]next[blank_end] neuron and make it [blank_start]less[blank_end] likely to [blank_start]fire[blank_end].

The knee-jerk reflex... 1. When a [blank_start]stimulus[blank_end] such as a hammer hits a knee, this is detected by [blank_start]sense[blank_end] [blank_start]organs[blank_end] in the [blank_start]somatic[blank_end] NS, in the [blank_start]Peripheral[blank_end] NS. 2. This causes a message to be sent via a [blank_start]sensory[blank_end] ([blank_start]afferent[blank_end]) neuron towards the [blank_start]spinal[blank_end] [blank_start]cord[blank_end] in the [blank_start]Central[blank_end] NS. 3. This message [blank_start]connects[blank_end] with a relay neuron which [blank_start]transfers[blank_end] it to a [blank_start]motor[blank_end] ([blank_start]efferent[blank_end]) neuron. This then carries the message to an [blank_start]effector[blank_end], such as a [blank_start]muscle[blank_end], which causes the muscle to [blank_start]contract[blank_end], hence the knee jerks.