The nervous System

The central nervous system is the brain and spinal column. The spinal cord's purpose is to relay information between the brain and the rest of the body which allows the brain to monitor and regulate bodily processes. It is connected to different parts of the body by pairs of spinal nerves containing cells. 

The brain can be divided into four main areas: cerebrum - divided intofour lobes and split into two halves which are speicalised for behaviours and communicate. Cerebellum controls a person's motor skills and balance. Diencephalon  - Thalamus is a relay station and the hypothalamus controls the release of hormones. Brainstem is responsible for regulating the automatic fucntions. 

The peripheral nervous system relays nerve impulses from the CNS to the rest of the body.

Somantic Nervous System: contain sensory and motor neurons. sensory neurons relay messages to the CNS, and motor neurons relay information from the CNS.

Autonomic Nervous System: involuntary actions are regulated by the ANS - it is necessary for bodily functions to work effeciently.

- Sympathetic Nervous System: helps us deal with emergencies. Neurons from the SNS travel to virtually every organ and gland, to prepare for rapid action. 

- Parasympathetic Nervous System: relaxes the body again once the emergency has passed. it slows the heartbeat down and reduces blood pressure. 

Neurons are cells that are specialised to carry neural information throughout the body. neurons consist of a cell body, dendrites and an axon. Dendrites at one end of the neuorn recieve signals from other neurons. from the cell body, the impulse is carrid along the axon, where it terminates. The myelin sheath allows nerve impulses to transmit more rapidly along the axon. 

It must cross the pre-synaptic neuron and the post-synaptic neuron, at the end of the axon there are vesicles which contains chemical messages which are impulse and transmitted in the neurotransmitters. once released it diffuses across the gap it binds to the speicalised receptors on the surface of the cell is then activated. 

Excitatory neurotransmitters: act as on switches and increase the likelihood of singals.

Inhibitory neurotansmitters: are the nervous system's off switches, in that they decrease the likelihood of the neuron firing. 

Endocrine glands: produce and secrete hormones, chemical substances that regulate the activity of cells or organs in the body. Each gland in the endocrine system produces different hormones, which regulate the activity. A singal is sent from the hypothalamus to the pituitary gland which when stimulated a hormone is secreted into the bloodstream. Hormones are chemicals that circulate in the bloodstream  and are carried to target sites throughout the bodyTarget cells respond to a particular homrone because they have receptor cells.

Pituitary gland: produces hormones which influence the release of hormones from ohter galnds and regulate bodily functions. it produces hormones that travel in the bloodstream. Anterior (front) releases ACTH as a response to stres. Posterior releases oxytocin which stimulates contractions.

Adrenal glands: the adrenal cortex produces cortisol which supports many functions. The adrenal medulla releases adrenaline and noradrenaline which prepare the body for fight or flight. Ovaries: are responsible for production of eggs and progesterone (post ovulating phase).Testes: are the male reproductive glands that produce the hormone testosterone controlled by the hypothalamus. 

Amygdala sends a distresss signal to the hypothalamus, which function like a command centre. 

Acute: SNS is triggered, it begins the process of preparaing the vody for rapid action necessary and sends a signal through to th adrenal medulla releasing adrenaline. Adrenaline causes a number of changes as the heart beats faster and breathing is more rapid to take in more oxygen. The PNS dampens down the stress response and digestion begins again. 

Chronic: H - hypothalamus relases a chemical messenger CRH which is releases into the bloodstream. P - it causes the pituitary produces and releasers ACTH which is transported to target site adrenal glands. A - ACTH stimulates the adrenal cortex to releases stress related hormones including cortisol .

Motor cortex is responsible for voluntary motor movements. it is located in the frontal lobe.

Somatosensory cortex detects sensory events, it is located in the parietal lobe. 

Visual centres: is located in the visual cortex, in the occipital lobe. Nerve impulses from the retine are transmitted through the brain via the optic nerve. The left hemisphere is responsible for visual field while the right hand recieves input from the left. 

Auditiory centres: are concerned with hearing. It is located in the temporal lobe as auditory pathways begin in the cochlea where sound waves are converted into nerve impluses them, then from the brain stem to the thalamus to the auditory cortex.

Broca's area: Was a neurosurgeon who treated a patient was able to understand language though was unable to speak. He had lesions in the left frontal hemisphere.

Wernicke's area: Was a neurologist. Wernicke's area could speak but were unable to understand language. The sensory region was responsible for auditory and visual input.

Lateralisation refers to two halves of the human brain. Each hemisphere has functional specialisations. The left hemisphere is dominant for language and speech, whereas the rgiht excels at visual-motor tasks. The two hemisheres are connected by the corpus callosum which allow the two to communicate with each other.

Sperry and Gazzangia: the split brain patient would fixate on a dot in the centre of a screen while information was presented to either the left or right visual field. They would then be asked to make repsonses with either their left hand or the right hand or verbally. If the patient was flashed a picture of a dog to the right visual filed and asked what they had seen, they would answer dog. If a picture of a cat was flashed to the left visual field the patient would say that he or she sees nothing. 

Plasticity: when people gain new experiences, nerve pathways that are used frequently develop stronger connections, wheras neurons that are rarely or never used eventually die. They constantly adapt though there is a natural decline. Boyke found brain plasticity in 60 year olds taught a new skill. Kuhn compared two groups playing super mario for two months, 30 mins every day, finding increase grey matter. Davidson compared eight practitionares and 10 student volunteers fitted to electrical sensors ans asked to meditate. The electrodes pickrd up much greater activiation of gamma waves in the monks.

In the 1960's, researchers studied cases in which stroke victims, were able to regain functioning. Over time the brain re-wires itself though it may be damaged other parts take over and form new circuits. 

Neuronal unmaksing - dormant synapses, when increasing the activity they start to open up. Stems cells - are unspecialised cells that have the potnetial to give rise to different cell types that carry out different functions. Stem cells might work to provide treatments through implant or transplanted. 

Our circadian rhythms are driven by our body clocks, found in all of the cells of the body, and synchronised by the master circadian pacemaker, the SCN is found in the hypothalamus. Light provides input and uses brightness detectors to coordinate information of the clock. 

Sleep-wake cycle: light and darkness are the external signals that determine when we feel the need to sleep and wake up. There are two dips at 2-4am and 1-3pm. When we have been awake for a long period of time, homeostasis tells us that we need to sleep to increase energy. 

Core body temperature: it is at its lowest at 4:30am and at its highest at 6pm. Sleep occurs when the core temperature begins to drop and body temperature starts to rise during the last hours of sleep, promoting feeling of alertness. 

Homrone production: the production and release of melatonin from the pineal gland in the brain follows a circadian rhythm, with peak levels occuring during the hours of darkness as it encourages feelings of sleep. 

Ultradian:

Sleep follows a pattern of REM and NREM sleep which repeats every 90-100 minutes of 4 NREM stages and 1 REM stage. As the person enters deep sleep, their brainwaves slow down and their breathing and heart rate decreases. BRAC is a 90 minute cycle in the day. It starts with a stae of alertness and as we run out of resources, resulting in loss of concentration.

Infradian:

Weekly rhythms - male tesosterone lvels are elevated at weekends and frequency of briths at weekends is lower than on weekdays. 

Monthly rhythms - menstrual cycle lasts about one month it is regulated by hormones, which either promote ovulation or stimulate the uterus for fertilisation.

Annual rhythms - in most animals they migrate as a response to lower temperatures. there is a seasonal variation in mood in humans, especially in women. Some people become very depressed during the winter months and more human deaths are in Janurary.

Endogenous: The SCN lies in the hypothalamus and acts as a master clock, linking to brain regions. Neurons synchronise to target sites to maintain the rhythm which works as it only needs resetting when external light levels change. The Scn sends signals to the pineal gland, directing it to increase production and sectretion of the hormone melatonin at night and to decrease it as light levels increase in the morning. Melatonin induces sleep by inhibiting brain mehcanisms that promote wakefulness.

Exogenous: receptors in the SCN are sensitive to hcanges in light levels furing the day and use this information to synchronise the activity or organs and glands. rods and cones in the retina of the eye detect light form visual images. Melanoopsin carry signals to the SCN to set the daily bodily cycle. 

Social cues also play a role in how our rhythms are constructed. Sucg as jetlag those who adjusted better where those who went outside more often as they were exposed to social cues or meal time and social acitivites.