Recently in Medicine Category

Swansea-Gambia Link Project 2010

A group of students are out in the Gambia looking at health in the context of international development. If you want to find out more and keep up with what they're doing, take a look at their blog:

swanseagambialinkproject2010.blogspot.com

Neuroscience podcast 4: autonomic nervous system

Phil & I recorded another neuroscience podcast. Number 4 covers the autonomic nervous system and we talk about the anatomy, the wiring of the neurones, and the neurotransmitters involved.

I might have to listen to that neurotransmitters section a few more times.

MP3: Neuroscience podcast 4 - autonomic nervous system.

iTunes: Neuroscience podcast 4 - autonomic nervous system (enhanced format).

Anatomy & embryology podcast 24

OK, I finally finished the latest podcast in which Rhiannon and I talk about what we think are the important aspects of the anatomy of the lower limb. This is the first part of two, and is 45 minutes long. We talk about the bones of the foot and ankle, the knee, the sciatic nerve, veins, and compartments of the leg. We've got another 5 topics to talk about in episode 25.

Get it from iTunes or from the Medicine page. The iTunes enhanced version has a bunch of images in it.

Anatomy: the lumbosacral plexus and the lower limb

On Monday we started looking at the structure of the hip, the muscles there and the nerves involved in motor and sensory innervation. In my station we talked about the lumbosacral plexus. Lots of nerves!

A nerve plexus is merely a lot of separate nerves (it's probably best to think of long, individual nerve cells) coming together into a group and then separating off towards different destinations. Some nerves from different spinal roots run off to those destinations together. It's like cabling in a building. There are no connections between nerves in a plexus.

We said that the lumbar plexus + sacral plexus = lumbosacral plexus. You may read that the coccygeal plexus is involved too, and yes, the coccygeal nerve (the last pair of spinal nerves!) links with sacral nerves.

[Need to review the spinal cord? Check here (missing coccygeal nerve) and here].

The roots of the lumbar plexus are formed by spinal nerves L1-L4. Remember that the posterior rami pass to the back muscles, so the lumbar plexus is formed from anterior rami. The lumbar plexus lies deep to and within the psoas muscles, and the nerves will pass on to the lower limb and the lower part of the abdomen.

The nerves L4 and L5 come together to form the lumbosacral trunk. This links to the sacral plexus, joining the two plexuses and making it easier for us to take them together as the lumbosacral plexus.

The sacral plexus forms from the spinal nerves S1-S5 an lies upon the piriformis muscle. The major nerve from the sacral plexus is the pudendal nerve (S2-S4, main sensory nerve for external genitalia and motor to muscles of continence including the external urethral and anal sphincters and levator ani - these also receive other motor innervation though). The sacral plexus also forms many tiny, short nerves that directly innervate the muscles of the hip that the plexus lies on or near. As such these nerves may be difficult to identify but they exist, for example, the nerve to obturator internus (and gamellus superior) and the nerve to quadratus femoris (and gamellus inferior). Confusing? Sorry.

The nerves of the lumbosacral trunk are combined with the sacral plexus to form the sciatic nerve (L4-S3). This giant nerve running out through the greater sciatic foramen and into the gluteal region descends the length of the posterior lower limb, innervating the posterior compartment of the thigh and all the muscles distal to the knee. It splits into tibial and common fibular (or peroneal) nerves before it reaches the popliteal region behind the knee. This monster nerve, along with the superior gluteal nerve (L4-S1) and inferior gluteal nerve (L5-S2) is the reason why we consider the lumbar and sacral plexuses together. The number of spinal nerves contributing to the sciatic nerve (and the lumbar location of those roots) suggest that it is more likely to suffer impingement than any other nerves. I'm sure that most of you will be aware of sciatica. As the sciatic nerve passes into the gluteal region and is very large you must be aware of its location if you're considering sticking needles into someone's bum.

We didn't talk about the parasympathetic nerves arising within the pelvis, so we'll pick those up in other, pelvic-related weeks. The pudendal nerve also takes a very interesting route to reach its destination outside the pelvis, which we'll also discuss in other sessions.

So, the lumbosacral plexus is formed from the anterior rami of spinal nerves L1-S5. The most important nerves to watch out for are probably those mentioned above, the lumbosacral trunk is the link, and the sciatic nerve (and gluteal nerves) is the main reason for the link. Make sure you can link these plexuses and nerves into your understanding of the abdomen, pelvis and lower limb.

Neuroscience podcast no. 3 - Neurotransmitters

Phil tried really hard to teach me about neurotransmitters in our most recent podcast. We talked about how they work and went through a list of the key neurotransmitters and gave an overview of what they do. Many of them will be talked about in more detail in future podcasts!

My poor brain.

MP3: Neuroscience podcast - No.3 Neurotransmitters.

iTunes: Neuroscience podcast - No.3 Neurotransmitters (iTunes).

46 days post-fracture

Messy, huh?

Neuroscience podcast no. 2

Another neuroscience podcast is out: Phil tells me why my weight is fairly stable, what happens in my brain when I get hungry and what changes when I have eaten. We talk about the adipostat, leptin, ghrelin and obesity, why we choose particular foods and how dopamine, opioids and (probably) serotonin are involved.

MP3: Neuroscience podcast - No.2 Neurobiology of appetite regulation.

iTunes: Neuroscience podcast - No.2 Neurobiology of appetite regulation (iTunes).

X-ray at 18 days.

For interest. This oblique view is more telling than the A-P.

New neuroscience podcast!

Phil Newton (henceforth to be known as Dr Phil) and I have begun a new podcast series to help medical students and others in similar need learn about neuroscience. Phil intends the series to be complementary to the lecture series in Swansea, but it should be useful and maybe even interesting to students anywhere.

In the first episode Dr Phil teaches me about action potentials and how neurons signal other neurons. Its about 35 minutes long and you can subscribe to the podcast in iTunes or download the MP3s from this blog or Dr Phil's.

MP3: Neuroscience podcast - No.1 Action potentials and synapses.

iTunes: Neuroscience podcast - No.1 Action potentials and synapses (iTunes).

Podcast episode 23

A new podcast is up on iTunes and the medicine page of my blog. Rhi and I finish talking about our list of things med students really should know about the anatomy of the pelvis. We include the vas deferens and the urethra, the os, the organs of the female pelvis and their ligaments, and sensory innervation from external genitalia.

Links:

- Subscribe in iTunes

- Download the MP3: Episode 23: 10 things you should know about the anatomy of the pelvis (part 2).

Cell Size & Scale

Do you struggle with the concept of scale, like I do? How small is a red blood cell compared with a grain of salt? How big is a virus? What does a glucose molecule look like to a cell?

Try this:

http://learn.genetics.utah.edu/content/begin/cells/scale/

Heart sounds, podcast

Are you learning to recognise heart sounds, or revising? Go to iTunes U and have a listen to this Medical College of Georgia podcast:

Heart Sounds

This is a natural and great use for the podcast format, but you'll need some teaching to go with the sounds that you hear! As a simple anatomist I've no idea what these sounds mean, but you may find them useful.

The brain has crumple zones?

The brain's sulci seem to play a role in physical damage limitation. A study modelled the effects of impact on normal brains and gyri and sulci free brains. The smooth brains were more vulnerable.

Links:

Wired article
Ho J, Kleiven S. (2009). Can sulci protect the brain from traumatic injury?,
J Biomech. Aug 11, epub ahead of print.

Stress and Illness

A common theme on this website (and the reason for the domain name, "dontbeasalmon.net") is the link between stress and illness.

Here's a brief article on ScienceDaily.com: Starve A Fever, Feed A Cold, Don't Be Stressed. There are notes about the field of "psychoneuroimmunology" (which is a new one for me) and the study of the effects of stress upon our immune systems.

There are some interesting comments about cross-training psychology students in biology and physiology to aid future cross-discipline development. I'm surprised this doesn't already happen.

Drug testing

This is why drug testing scares me. A recent study, summarised in this slowtwitch.com article, demonstrated that athletes ingesting a mere 5ug of the nandrolone precursor 19-norandrostenedione (NOR) tested positive for this anabolic steroid using existing procedures. That's a tiny amount. It's a trace amount. It's an amount that you wouldn't ingest to improve your performance but the kind of amount that is considered a contaminant or trace element within another food.

Should governing bodies risk destroying an honest athlete's career with science we don't yet fully understand?

Links:

- SlowTwitch - How Much is Enough?
- PubMed abstract & links - Watson P., Judkins C., Houghton E., Russell C., Maughan R.J., Urinary nandrolone metabolite detection after ingestion of a nandrolone precursor. Med. Sci. Sports Exerc., Vol. 41. pp.766-72, 2009.